President Donald Trump said Tuesday in a Fox News interview that Iran is becoming "much more aggressive" in nuclear negotiations.

The day prior, Trump told reporters that the Iranians are "tough negotiators" and sought to clarify that he would not allow Tehran to enrich uranium on its soil, after some recent contradictory reports suggested the White House had backed off this demand.

Washington is awaiting a formal response from the Islamic Republic, which is expected to submit a counter-proposal in the coming days, just ahead of an expected sixth round of indirect talks with the US in Muscat, Oman, slated for Sunday, June 15.

"Iran is acting much differently in negotiations than it did just days ago," Trump told Bret Baier. "Much more aggressive. It’s surprising to me. It’s disappointing, but we are set to meet again tomorrow — we’ll see."

And previously, on Monday, the president had this to say:

"They’re just asking for things you can’t do. They don’t want to give up what they have to give up," Trump told reporters at the White House. "

"They seek enrichment. We can’t have enrichment. We want just the opposite, and so far they’re not there. I hate to say that, because the alternative is a very, very dire one."

Iran's Ayatollah just last week made very clear that Tehran won't give up its enrichment program, which it says is only for peaceful nuclear energy purposes.

Trump has blasted this position as "unacceptable" and has warned that Tehran could face bombs if a deal isn't reached. This also as Israel is threatening potential preemptive strike.

But Iran has responded by warning that its advanced, long-range missiles could target Israel's secretive nuclear facilities if the Iranians come under attack.

Israel has for decades maintained an undeclared nuclear weapons program, which the United States has never formally acknowledged, also with the State Department consistently refusing to answer questions on it.

The nuclear arsenal is commonly estimated to be somewhere in the range of 90 to 300 warheads, and it being undeclared means it remains completely outside international oversight.

Regional Muslim-majority nations have long called out Western hypocrisy on the issue. Iran's nuclear energy program has been tightly monitored under the prior Obama JCPOA nuclear deal, and current talks with Washington aim to reestablish a similar monitoring regimen.

It was Trump himself who unilaterally pulled the US out of that deal in April 2018 - and this is a big reason why Tehran doesn't trust this current administration.