The White House's national security advisor, Mike Waltz, has said that the US sought "full dismantlement" of Iran's nuclear program.
"Iran has to give up its program in a way that the entire world can see," he said on CBS News on Sunday.
"As President (Donald) Trump has said, this is coming to a head. All options are on the table and it is time for Iran to walk away completely from its desire to have a nuclear weapon."
US special envoy Steve Witkoff also said Sunday that Trump's outreach to Iran's top authority, Supreme leader Ali Khamenei, on a possible new nuclear deal is an effort to avoid military action.
"We don't need to solve everything militarily," Witkoff told Fox News.
"Our signal to Iran is let's sit down and see if we can, through dialogue, through diplomacy, get to the right place. If we can, we are prepared to do that. And if we can't, the alternative is not a great alternative."
Trump said earlier this month that he had sent a letter to Khamenei, warning that "there are two ways Iran can be handled: militarily, or you make a deal."
Khamenei rejected the US offer for talks as "a deception," saying negotiating with the Trump administration would "tighten the knot of sanctions and increase pressure on Iran."
Also Sunday, Iran's foreign minister, Abbas Araqchi, said talks with the United States are no longer possible unless certain things change.
He said that Iran was not opposed to talks out of "stubbornness,” but rather as a result of history and experience, adding that Washington needs to recalibrate its policy before Tehran takes part in talks.
In his first term, Trump withdrew the United States from a 2015 deal between Iran and major powers that had placed strict limits on Tehran's nuclear activities in exchange for sanctions relief.
After Trump pulled out in 2018 and restored sanctions, Iran breached and far surpassed those limits in the development of its nuclear program.
"In my opinion, the 2015 pact in its current form cannot be revived. It would not be in our interest because our nuclear situation has advanced significantly and we can no longer return to previous conditions," Araqchi said. "The same can be said of the other side's sanctions. The 2015 nuclear pact can still be a basis and model for negotiations."
