Sen. Robert Menendez, D-N.J., left, and Sen. Bob Corker, R-Tenn., say Congress should play a role in shaping talks with Iran over its nuclear program. (Susan Walsh/AP)

A day after President Obama threatened to veto any sanctions bill against Iran, lawmakers on Wednesday clashed with top administration officials over U.S. strategy in nuclear talks with the Islamic republic and indicated that they would drive headlong toward tougher legislation.

The determination of a group of bipartisan lawmakers to pass measures they believe will raise pressure on Iran escalates a high-stakes battle with the Obama administration. The White House has warned that new sanctions will scuttle hopes of reaching an agreement with Iran and unravel an international coalition enforcing existing sanctions.

But members of Congress, including Obama’s nominal Democratic allies on foreign policy, expressed no willingness on Wednesday to cede the issue of how to best deal with Iran in the run-up to the July deadline for the talks.

Sen. Bob Corker (R-Tenn.), chairman of the Foreign Relations Committee, wants the administration to submit any final deal to Congress for approval. Other key lawmakers want legislation that would impose a series of escalating penalties should the talks fail. Still others suggested a nonbinding resolution stating Congress’s intent to impose crippling sanctions if negotiations fail. Whatever the approach, members from both sides of the aisle are insisting on a role in shaping the outcome of the talks, pushing back against the administration’s appeal to give diplomacy room to work.

“Over the past 18 months, we have been moving closer to their [the Iranians’] positions on all key elements,” said Sen. Robert Menendez, the ranking Democrat on the Foreign Relations Committee, at a testy three-hour hearing. “The more I hear from the administration in its quotes, the more it sounds like talking points that come straight out of Iran.”

Administration officials insisted that further sanctions or other pressure would only risk undermining the diplomatic effort by the world powers. “I know the intent is to further increase pressure on Iran and, in so doing, strengthen the hand of our negotiators,” Deputy Secretary of State Antony J. Blinken said. But, he said, the administration believes that additional sanctions are unnecessary at this time and “risk unraveling” the current sanctions regime. “Iran is well aware that the sword of Damocles hangs over its head,” he said. “It needs no new sanctions.”

Menendez, of New Jersey, has drafted legislation with Republican Sen. Mark Kirk of Illinois, who sits on the Banking Committee, that would not impose sanctions for the duration of the talks. But if the negotiations fail, the bill would reimpose sanctions lifted in the interim and escalate them in a series of steps.

The high emotions on display during the hearing suggest that both sides are girding for battle. As the hearing proceeded, on the other side of the Capitol, aides to House Speaker John A. Boehner (R-Ohio) announced that he is inviting Israel Prime Minister Benjamin Netanyahu to address a joint session of Congress on Feb. 11 on the threats posed by Iran and radical Islam. Netanyahu has been skeptical of the talks and has taken the position that any agreement should not leave Iran as a “nuclear threshold” country, one that could move to acquire nuclear weapons quickly.

“Clearly, there’s a majority in Congress in support of additional sanctions,” said Robert Einhorn, a senior fellow at the Brookings Institution and a former member of the U.S.team negotiating with Iran. “But whether they have the 67 votes to override a veto is another story. The administration will go all out to gain the necessary 34 votes to sustain a veto.”

Administration officials reiterated their position that an interim deal between Iran and six world powers in November 2013 has frozen Iranian nuclear activity in several key respects, including forcing the regime to reduce the size of its stockpile of enriched uranium. They said they are making progress toward a final agreement, even as “real gaps” remain.

“Overall, our assessment remains that we have a credible chance to reach a deal that’s in the best interests of America’s security, as well as that of our allies and partners,” Blinken said.

The goal he said is to reach agreement on core elements by the end of March, with an agreement on technical details by July. The elements would include provisions to cut off Iran’s pathways to obtain fissile material for a nuclear weapon; strict requirements of international access to facilities; and confidence that if Iran broke its commitments, it would take at least one year to produce enough fissile material for a bomb.

Officials said Iran’s economy has been severely hurt by financial, banking, oil and trade sanctions, whose impact was exacerbated by a steep drop in oil prices. “Iran is negotiating with its back against the wall,” said David Cohen, Treasury undersecretary for terrorism and financial intelligence.

Corker said that Iran is “still . . . stiff-arming” nuclear inspectors who are seeking access to Iranian facilities.

It is crucial, Corker said, for Congress to sign off on any final agreement. He said he has consulted international partners, including the French and British. “I have yet to talk to anyone who has said our weighing in would jeopardize the negotiations,” he said.

Corker threatened to pull the national security waivers that Congress granted the administration in sanctions legislation, which allow the president to waive sanctions if doing so is important to national security. Such waivers are key to any deal that would involve suspending sanctions at the president’s discretion.

Blinken said the administration’s concern is that Corker’s idea “could set a precedent for future executive branch action” and undermine the “executive prerogatives” to conclude agreements in national security without formal congressional approval.