"These contradictory remarks are either a sign of their confused policies or is a trick to confuse the other side," Ali Khamenei said Tuesday.
Hamad bin Jassim bin Jabor al-Thani said Iranians won't crack under American economic pressure, and will look to play the long game instead.
Russian foreign minister Sergey Lavrov said American pressure on the Iran nuclear deal is designed to create a pretense for conflict.
"It's not news that the U.S. and UK differ in how to ensure Iran is never able to acquire a nuclear weapon," a spokesman for the UK Foreign Office said.
"Iranian people have proved over the past 40 years that they are ready to pay for safeguarding national identity, territorial integrity, freedom, independence and Islamic establishment," Masoumeh Ebtekar said.
"The U.S. has destabilized security of the international system through unilateralism and extra-terrestrial sanctions," Ali Shamkhani said.
"The entire world recognizes the U.S. as a country reneging on its promises," President Hassan Rouhani said on Tuesday.
Enriched uranium is required to produce nuclear power, but at a higher level of enrichment it can also be used to build nuclear weapons.
"The Iranians should understand very clearly that we will continue to take actions that deter Iran from engaging in this kind of behavior," Secretary of State Mike Pompeo said.
"That's a very serious issue if they continue to do that," Trump's national security adviser warned.
"We are actually considering escalating with Iran in a war that would further destabilize the region and unleash God knows what in terms of chaos in a very troubled region already," Elise Jordan said.
Washington has been at odds with Europe over Iran since the Trump administration abandoned the 2015 nuclear deal.
"They have all shown an interest in dragging the United States into a conflict," Javad Zarif told Fox News Sunday. "I do not believe that President Trump wants to do that. I believe that President Trump ran on a campaign promise of not bringing the United States into another war."
"The rest of the world sees perfectly well that Washington's policy is getting increasingly aggressive and reckless," a Russian Foreign Ministry statement said.
Iran's General Amir Hatami said President Donald Trump's policies have promoted "such traits as selfishness, cruelty and violation of humanitarian principles and international rules."
The president "rejoices over the misery that he thinks he has imposed on ordinary Iranians," Iranian Foreign Minister Javad Zarif wrote on Twitter.
"No one can defeat a nation which pursues resistance," Iranian President Hassan Rouhani said in a televised address, claiming the U.S. and its allies were to blame for the country's poor economy.
Ayatollah Ahmad Khatami pointed out that nuclear bombs are "clearly" against Islamic (or Sharia) law.
"Iraq's constitution does not allow our territory of our country to be used against our neighbors," President Barham Salih said.
"We continue to assess that Iran is not currently undertaking the key nuclear weapons-development activities we judge necessary to produce a nuclear device," Dan Coats said.
"It definitely rattled people," a former senior U.S. administration official told The Wall Street Journal. "People were shocked. It was mind-boggling how cavalier they were about hitting Iran."
"The Americans happily say that these sanctions are unprecedented in history. Yes, they're unprecedented. And the defeat that the Americans will face will be unprecedented, God willing," Supreme Leader Ayatollah Ali Khamenei said.