Iranian President Hassan Rouhani speaks in parliament in Tehran on Dec. 4. (Vahid Salemi/Associated Press)

Sanctions against Iran were officially extended for another decade Thursday, even though President Obama did not sign the legislation, a symbolic move intended to show the White House’s disapproval of the bill.

The sanctions renewal, which passed Congress with enough votes to be veto-proof, has triggered complaints from Tehran. The Iranian government views the nuclear agreement as entailing a promise of no new sanctions. The White House, by not signing the bill, is trying to alleviate Iran’s concerns.

Secretary of State John F. Kerry said the nuclear deal is still a “top strategic objective” for the United States. With or without the sanctions renewed, he said, the United States could snap sanctions back into place if Iran were to violate the Joint Comprehensive Plan of Action (JCPOA), the formal name for the nuclear deal. Kerry said that even though he considers it unnecessary to renew the existing waivers, he had done so anyway “to ensure maximum clarity” that the United States will meet its obligations under the deal.

He also said he had contacted Iran’s foreign minister, Mohammad Javad Zarif, and U.S. allies to reassure them that the United States remains committed to the deal that gave Iran sanctions relief once it pared back its nuclear program.

“As long as Iran adheres to its commitments under the JCPOA, we remain steadfastly committed to maintaining ours as well,” he said.

Here's what's in the Iran nuclear deal, and what happens next. (Gillian Brockell and Julio C. Negron/The Washington Post)

But with President-elect Donald Trump just five weeks away from taking office, Kerry’s guarantees may be short-lived if the new administration takes a tougher approach to Iran, as is expected.

“President Obama doesn’t want to provide an excuse in the waning days of his administration for the Iranians to walk away from the deal,” said Mark Dubowitz, head of the Foundation for the Defense of Democracies and a prominent critic of the Iran deal.

“But at this point, he’s a lame-duck president, and what he does or does not do is completely irrelevant to the incoming administration and completely irrelevant to the Iranians.”

The Iran Sanctions Act extension passed unanimously in the Senate on Dec. 1.

It extends the president’s authority to impose sanctions, a measure the Obama administration insisted did not affect the U.S. commitment to the deal or its ability to provide sanctions relief to Iran.

The White House had said Obama would sign the bill into law, so his decision not to is a reversal.

But the Senate is expected to take even broader steps against Iran next year, imposing more punitive measures and leaving the deal’s fate in limbo.

Tehran has complained to the U.N. committee overseeing the deal’s implementation, saying the sanctions renewal is a “blatant contradiction” of what the parties that negotiated the deal agreed to.

In response to the vote in Congress, Iranian President ­Hassan Rouhani this week ordered the development of ­nuclear-powered ships, a step some analysts believe is more a show of swagger than a real threat. Iran is contemplating additional steps in response to the sanctions renewal, an adviser to Supreme Leader Ayatollah Ali Khamenei said Wednesday.

The rhetoric coming from Tehran underscores the uncertainty around the Iran deal’s very foundations as Washington prepares for the Trump presidency.

It is not clear whether Obama’s symbolic gesture of keeping his name off the legislation will succeed in calming Tehran or ensuring the nuclear deal’s fate.

“I think President Obama hopes to mitigate the Iranian response to President-elect Trump’s tougher rhetoric on the deal,” said James Phillips, a Middle East analyst at the Heritage Foundation. “The White House is acting as if it’s on life support.”

The impending change of power in Washington may have political implications for the Iranian officials who put their political futures on the line to get an agreement after more than a decade of negotiations.

Rouhani, whose administration pushed the deal forward as a way to end Iran’s economic isolation, is up for reelection in March.

Some Iranians have complained that they are not seeing the economic benefits they expected from the nuclear deal, which could harm him at the polls. Iranian critics of the deal already have characterized him as being outmaneuvered by the Americans.

“By the middle of 2017,” said Trita Parsi, head of the National Iranian American Council and a supporter of the deal, “you could have a president in Iran and a president in the United States who both ran on the same platform opposing the nuclear deal.”