Update(10:30ET): With President Trump and his envoy having arrived in the United Arab Emirates (UAE) for the last leg of the president's Gulf tour, new details of behind the scenes US-Iran negotiations have come to light on Thursday.

In a huge first, the Trump White House has sent Iran a written proposal toward forging a new nuclear deal. White House envoy Steve Witkoff has led several rounds of talks, and Axios has revealed that the communication was issued to Tehran last Sunday.

"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," writes Axios.

It was the Iranian side which initiated the swap of written proposals first, as the talks which have been on since April went from 'indirect' to more 'direct':

• 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 U.S. 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.