The Trump administration gave Iran a proposal for a nuclear deal during the fourth round of negotiations on Sunday, a US official and two other sources with direct knowledge tell Axios, the latter reports.

It was the first time since the nuclear talks started in early April that White House envoy Steve Witkoff presented a written proposal to the Iranians.

Iranian Foreign Minister Abbas Araghchi took the proposal back to Tehran for consultations with Supreme Leader Ali Khamenei, President Masoud Pezeshkian and other top officials.

US President Trump said Tuesday in Saudi Arabia that he'd presented "an olive branch" to the Iranians but stressed "this is not an offer that will last forever. The time is right now for them to choose.”

During the first round of talks, Araghchi gave Witkoff a written document with several Iranian proposals. Witkoff told Araghchi it was too soon for that and he wanted to build rapport first, a source with knowledge of that meeting said.

During the third round of talks in late April, Araghchi gave Witkoff an updated document with Iranian ideas for a nuclear deal. This time, Witkoff took the document.

A US team of experts studied it and sent the Iranians a list of questions and requests for clarification. The Iranians replied and added questions of their own, two sources said.

Meanwhile, Witkoff and his team prepared a U.S. proposal laying out the Trump administration's parameters for an Iranian civilian nuclear program and requirements for monitoring and verification, the sources said.

In a briefing with reporters on Thursday Trump said the U.S. is close to a deal with Iran and stressed the talks that are taking place "are very serious.”