U.S. President Donald Trump is reportedly open to giving economic sanctions relief and release frozen funds to Iran in exchange for concrete progress related to its nuclear program, a U.S. official told American news outlets Axios and CNN on Monday.

Washington is engaging in "positive and constructive" talks via mediators, CNN quoted a U.S. official as saying, emphasizing that negotiators would not finalize an agreement unless nuclear-related concerns received full resolution.

The White House did not immediately respond to a request by Anadolu Agency (AA) for comment on the remarks.

The prospective diplomatic opening comes after Trump on Saturday rejected an Iranian proposal aimed at easing tensions and reopening the strategic Strait of Hormuz, calling Tehran's conditions "unacceptable" amid the seven-month Iran war.

Trump said Sunday that he expects additional negotiations with Tehran this week, asserting that Iranian officials "overplayed" their hand during earlier talks.