WASHINGTON - US president's special envoy Steve Witkoff has said the Trump administration is demanding that any future nuclear deal remain in effect indefinitely, online media outlet Axios reported on Wednesday.

"We start with the Iranians with the premise that there is no sunset provision. Whether we get a deal or not, our premise is: you have to behave for the rest of your lives," Witkoff was quoted as saying at a private gathering in Washington, D.C. on Tuesday.

Witkoff said that two key issues in the current nuclear talks are Iran's ability to enrich uranium and the fate of its existing stockpile of enriched uranium.

He added that the talks were currently focused on Iran's nuclear program. However, if a deal is reached, the White House would seek follow-up negotiations on Iran's missile program and its support for proxy militias, said the report.

Under the 2015 nuclear deal reached during the presidency of Barack Obama, most restrictions on Iran's nuclear program were set to expire between eight and 25 years after the deal was signed. Iran also pledged never to pursue a nuclear weapon.

President Donald Trump, who scrapped the 2015 deal, could be open to "token" enrichment in Iran if Tehran proves it won't enable the development of a nuclear weapon, said the report, citing US officials who noted that Iran is currently under significant pressure from mediators -- Oman, Qatar, Egypt and Turkiye -- to move towards a deal with the United States that would prevent war.

A new round of US-Iran talks is now scheduled for Thursday in Geneva and expected to focus on Iran's nuclear program, including uranium enrichment levels and sanctions relief.

The US administration has been deploying massive military forces in the Middle East. Trump warned on Monday that he would rather reach a deal with Iran, but if one is not reached, "it will be a very bad day" for the country, referring to a potential US strike.