WASHINGTON — President Barack Obama on Friday left open the door to “creative negotiations” in response to Iran’s demand that punishing sanctions be immediately lifted as part of a nuclear deal, even though the initial agreement calls for the penalties to be removed over time.

Asked at a White House news conference whether he would definitively rule out lifting sanctions at once as part of a final deal aimed at keeping Iran from developing a nuclear weapon, Obama said he didn’t want to get ahead of negotiators in how to work through the potential sticking point. He said his main concern is making sure that if Iran violates an agreement, sanctions can quickly be reinstated.

“How sanctions are lessened, how we snap back sanctions if there’s a violation, there are a lot of different mechanisms and ways to do that,” Obama said.

He said part of the job for Secretary of State John Kerry and the representatives of five other nations working to reach a final deal with Iran by June 30 “is to sometimes find formulas that get to our main concerns while allowing the other side to make a presentation to their body politic that is more acceptable.”

Iran’s Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani insisted last week they would not sign a deal unless it lifts all sanctions on its first day.

Obama initially portrayed their comments as a reflection of internal political pressure, while pointing out the initial framework agreement reached earlier this month allows for sanctions to be phased out once international monitors verify that Tehran is abiding by the limitations.

Obama, speaking Friday at a news conference with Italian Prime Minister Matteo Renzi, said the sanctions issue “will require some creative negotiations by John Kerry and others.”

Obama also said he would sign legislation expected to pass the Senate and House giving Congress a say on a final deal, calling it a “reasonable compromise” that addresses his previous objections over Congress interference.

The legislation would block Obama from waiving congressional sanctions against Iran for at least 30 days after any final agreement, which would give lawmakers time to weigh in.