The United States is willing to sit down with Iran “tomorrow” and jointly agree to full compliance with the nuclear accord they and five other world powers signed in 2015, according to a senior Biden administration official.

“We’ve made clear that we’re not talking about renegotiating the deal,” the official said of the agreement that curbed Iran’s nuclear program in exchange for lifting U.S. and other sanctions.

Iran has made equally clear it shares the goal of going back to the terms of the original agreement, before President Donald Trump pulled out of it. Trump reinstituted the sanctions and added what Biden officials estimate were at least 1,500 new ones. In response, Iran reactivated key elements of the program the United States and others say could produce nuclear weapons. Iran denies any such ambition.

But nearly two months into Biden’s presidency, with Iran’s own contentious presidential election approaching in June, the two sides have been unable even to talk to each other about what both say they want.

There was a near miss more than three weeks ago, when the administration said it would attend a meeting called by the European Union with Iran and the other original signatories still party to the agreement — Britain, France, Germany, Russia and China. Iran said no, indicating it wanted to know more about what was on the table.

Since then, the United States and Iran have issued sometimes contradictory, often intransigent statements that reflect mutual suspicion and agendas that are far broader than the simple reactivation of an agreement that many opponents of their efforts say was flawed to begin with.

This report is drawn from public pronouncements from Washington and Tehran and interviews with a half-dozen senior U.S. and European officials and with experts familiar with the issue. The officials spoke on the condition of anonymity about what one called the sensitive, and halting, diplomatic “dance.”

Iran wants all Trump sanctions lifted and an immediate influx of cash from the release of blocked international loans and frozen funds, along with foreign investment and removal of bans on oil sales. It seeks assurances that the next U.S. administration won’t jettison the deal again.

Even when the nuclear agreement was in force, Iran complained that U.S. threats limited foreign investment. Sanctions during the first two years of Trump’s “maximum pressure” campaign led to the contraction of Iran’s economy by almost 12 percent, and oil exports — a key source of foreign currency — dropped by 80 percent, according to an analysis of the campaign published Thursday in Foreign Affairs by Hadi Kahalzadeh, a former Iranian government economist who is a PhD fellow at the Crown Center for Middle East Studies at Brandeis University.

Trump restrictions on Iran’s banking system impeded its ability to import medicine and medical supplies as the government confronted one of the worst coronavirus outbreaks in the world.

For its part, the Biden administration wants a reactivated deal, known as the Joint Comprehensive Plan of Action, or JCPOA, to serve as a “platform” to renegotiate its sunset provisions — the future dates when certain provisions are set to expire. It wants to move quickly to discussions about its other problems with Iran, including Tehran’s ballistic missile program and its use of proxy forces in Iraq, Syria and beyond, and human rights abuses.

And, although it hopes to keep the subject separate from the nuclear talks, it wants four Iranian American citizens imprisoned by Iran to be returned, along with information about former FBI agent Robert Levinson, who disappeared in Iran 14 years ago last week.

“We are talking about both sides returning into compliance . . . and only then engaging in follow-on negotiations on strengthening and lengthening the deal and addressing other concerns, knowing that Iran will bring its concerns to the table, too,” the senior official said.

The administration has not made clear whether an Iranian commitment to follow-on talks is a prerequisite to reentering the deal.

But even an agreement to take simultaneous, sequential steps to comply with its original terms requires a meeting, the official said.

“We can’t guess what steps they will take and when, and what steps we will take and when, without talking directly or — if they refuse — indirectly.”

Among the issues to discuss are which Trump sanctions — some of them unrelated to nuclear issues and thus not included in the original agreement — are eligible to be lifted.

Iran has said that it wants all sanctions gone and that it has no interest in talking about anything else. It maintains a right to develop ballistic missiles it insists are not intended for nuclear weapons, but for defense in a region where it is surrounded by adversaries. It shows no willingness to withdraw support for proxy forces in Iraq or elsewhere.

If the United States is willing to reenter with no conditions, then no meeting is required, Abbas Araqchi, Iran’s deputy foreign minister and nuclear negotiator, said in a Russian television interview Thursday. “Did the Americans hold talks with anyone when they withdrew from the agreement? Did they hold a meeting?” he said.

Washington has not taken any practical steps to implement its desire to rejoin, President Hassan Rouhani said in a phone call last week with British Prime Minister Boris Johnson, according to Iran’s PressTV.

“If we are after diplomacy, the path is clear,” Rouhani said, indicating the United States has to act first. “It’s the lifting of sanctions and the U.S. fulfilling of its commitments, and there is no other option.”

In public, both sides continue to wait for the other to prove its good faith with “you, first” rhetoric. Tehran has strongly hinted at a gesture that might break the deadlock — access to its funds frozen in South Korean banks because of U.S. sanctions. The money, said to total $7 billion from earlier oil purchases — would pass through Switzerland and be restricted to purchases of humanitarian goods such as medical devices, Iranian officials have said.

Late last month, however, Seoul said it would act only after “consultations” with the Biden administration. On Wednesday, Secretary of State Antony Blinken told lawmakers seeking assurances the administration would make no concessions that the ball remained in Iran’s court.

“Unless and until Iran comes back into compliance,” he said, “they won’t be getting that relief.”

Iran’s foreign minister, Mohammad Javad Zarif, charged that Trump’s maximum pressure remained alive and well. Blinken, he wrote on Twitter, “boasts [about] blocking Korea from transferring our OWN money to the Swiss channel. . . . Repeating the same policy won’t yield new results.”

Inside Iran, there is still optimism that the United States will make some sort of bold gesture to break the impasse, despite having “dallied for six weeks,” said Esfandyar Batmanghelidj, the founder and CEO of the London-based Bourse & Bazaar Foundation, a think tank focused on Iran’s economy.

In the sometimes convoluted reading of tea leaves by both sides, recent U.S. moves seen in Iran as bellicose — such as flying B-52 bombers over the Middle East and airstrikes against Iranian-allied militias in Syria — could be “preparatory steps for something conciliatory,” Batmanghelidj said.

Seeking its own reason for optimism, the administration was encouraged by what it saw as a signal sent this month by Zarif, who tweeted March 5 that he would “shortly present our constructive concrete plan of action — through proper diplomatic channels.”

Asked Friday about the status of any talks, Biden national security adviser Jake Sullivan told reporters that “there are communications through the Europeans and others that enable us to explain to the Iranians what our position is . . . and to hear what their position is. And we’re waiting at this point to hear further from the Iranians how they would like to proceed.”

The delays and obfuscations have frustrated all sides, including those within and outside the administration who believe weeks have been wasted.

“Iran is overplaying its hand,” a senior European official said, and the Americans “don’t want to offer anything until they have an overall plan. Okay, but some things are urgent.”

Iran has increased both the quantity and quality of its enriched uranium, from the 3.87 percent enrichment stipulated in the nuclear deal to 20 percent. The administration assesses that its “breakout” time — the moment when it has assembled enough fissile material to build a bomb — has shortened to about three months, down from a year when the agreement was being observed.

After threatening to significantly curtail the international monitoring and verification in effect under the deal, Tehran agreed in recent weeks to temporarily preserve key elements of the supervision, in exchange for a pullback in European plans to condemn its activities through the International Atomic Energy Agency.

Both U.S. and European officials are divided over the significance of the upcoming Iranian elections, in which the nuclear deal will be a central issue. Some are certain that a hard-line victory will lessen the chances of a return to an agreement that was originally signed by Rouhani, seen as a relative moderate. Others say that the only opinion that matters is that of Supreme Leader Ali Khamenei, who expressed skepticism about the original agreement and has now demanded “action, not words” from Biden.

Biden has his own hesitation about trusting the Iranians and appearing desperate for a deal, even as he is under pressure from many directions.

In December, 150 Democrats called on him to lift sanctions and unconditionally return to the 2015 accord. Last week, 70 Republicans and 70 Democrats signed a letter calling for a renegotiated, comprehensive new deal covering Iran’s nuclear program, ballistic missiles, terrorism and human rights violations.

Among allies, “some wanted the United States to move faster,” a second European official said. “But the question is how [Biden] can do that domestically,” even as he balances other foreign policy priorities, particularly in the Middle East, where the Iran issue is linked to Israel, Syria, Saudi Arabia and others.

For now, the president is biding his time. “We could go tomorrow,” the senior administration official said. “But we’re not going to cut corners in getting it right.”

Fahim reported from Istanbul.