Barack Obama said it was unrealistic to expect that any deal between U.S. President Donald Trump and Tehran would mark a "significant improvement" over his own nuclear pact 11 years ago.

In interview excerpts released Sunday on ABC News talk show "This Week," the former President also suggested it was better to negotiate a deal that falls short of all of Washington's requirements in order to avoid an outright war.

"It is doubtful that any agreement that arises is going to be significantly different or a significant improvement from the deal that we had in the first place," Mr. Obama said, referring to 2015's landmark pact that Mr. Trump abandoned.

Mr. Obama said his own deal "had worked for a long stretch of time before... the United States pulled out of it."

US and Israeli forces sparked the Middle East war in late February when they launched strikes against Iran. For months Trump has bandied about a potential peace deal with the Islamic republic, but that country's leaders have yet to sign on.

Mr. Trump has stressed the deal, which he says would forever block Iran's ability to produce a nuclear weapon and would lead to the immediate opening of the blockaded Strait of Hormuz, could be signed on Sunday.

Tehran has not confirmed it will yet sign a deal, saying that for now there was "no point" in peace talks with the United States.

Mr. Obama said the troubled progress of a new U.S.-Iran deal is a reminder that Washington can not "just bully our way or bomb our way to solutions" instead of engaging in comprehensive diplomacy.

"You'd think we would have learned that lesson by now," he said.