U.S. President Donald Trump’s outreach to Iran’s top authority, Supreme leader Ayatollah Ali Khamenei, on a possible new nuclear deal is an effort to avoid military action, U.S. special envoy Steve Witkoff said on Sunday.

“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 U.S. offer for talks as “a deception,” saying negotiating with the Trump administration would “tighten the knot of sanctions and increase pressure on Iran.”

However, Iran’s foreign minister, Abbas Araqchi, said on Thursday that Tehran would soon reply to both the letter’s “threats and opportunities.” He cautioned on Sunday that talks with the U.S. are impossible unless Washington changes its pressure policy.

Speaking separately on CBS News, the White House’s national security advisor, Mike Waltz, said the U.S. 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.

“As President 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.”

Tehran has long said the program is only for peaceful purposes.

U.N. nuclear watchdog chief Rafael Grossi said last month that time is running out for a deal to rein in Iran’s nuclear program as Tehran continues to accelerate its enrichment of uranium to near weapons grade.

While leaving the door open for a nuclear pact with Tehran, Trump has reinstated the “maximum pressure” campaign he applied in his first term as president, including efforts to drive the country’s oil exports to zero.

The U.S. has issued four rounds of sanctions on Iran’s oil sales since Trump’s return to the White House on January 20.