No nuclear weapons and don't kill your protesters, Trump warns Iran

US President Donald Trump on Sunday warned the Iranian regime not to "kill demonstrators" who took to the streets after the government admitted it had "unintentionally" shot down a Ukrainian passenger jet earlier last week.

"National Security Adviser suggested today that sanctions and protests have Iran "choked off", will force them to negotiate. Actually, I couldn't care less if they negotiate. Will be totally up to them but, no nuclear weapons and "don't kill your protesters," Trump said on Twitter.

His comments came after Robert O'Brien said on "Fox News Sunday" that Iran would soon have "no choice" but to engage diplomatically with the Trump administration, arguing that new sanctions passed were successfully ramping up the pressure on Tehran.

"I think the maximum pressure campaign is working," O'Brien said. "Iran is being choked off and Iran is going to have no other choice but to come to the table."

"What's going to cause them to negotiate is the pressure on the economy, and when you've got students out there chanting 'death to the dictator,' and when you have thousands of Iranians out protesting in the street, that's the sort of pressure that's going to bring them to the table," he added.

Iran and the US appeared to be at the edge of military conflict last week after the killing of Qasem Soleimani, head of Iran's Quds forces, for which Iranian forces responded with a barrage of missiles aimed at two Iraqi bases housing US troops, though the strikes caused minimal damage and no casualties.

Trump appeared to back off from talk of war this week in a public address to the nation, saying on Wednesday: "I'm pleased to inform you, the American people should be extremely grateful and happy. No Americans were harmed in last night's attack by the Iranian regime."

"Our great American forces are prepared for anything," he added.

"Iran appears to be standing down, which is a good thing for all parties concerned and a very good thing for the world," the President told his nation.