US President Donald Trump said that Iran had been "playing games" with the US and the "the rest of the world", in a long social media post on Sunday.
Days after the US submitted a proposal to Iran with hopes of ending the current conflict, Mr Trump wrote on his Truth Social platform: "For 47 years the Iranians have been 'tapping' us along, keeping us waiting, killing our people with their roadside bombs, destroying protests, and recently wiping out 42,000 innocent, unarmed protesters and laughing at our now great again country.
"They will be laughing no longer."
He blamed the Joint Comprehensive Plan of Action (JCPOA) between world powers and Iran, which Mr Trump essentially cancelled during his first term in the White House, for the current conflict. It was signed in 2015 under former president Barack Obama
"He was not only good to them, he was great, actually going to their side, jettisoning Israel and all other allies, and giving Iran a major and very powerful new lease on life," Mr Trump said.
Just a few hours before he posted, Iranian news agency Irna said that the country had sent a response to the latest US proposal for ending the war to Pakistan, which has been mediating between the two.
Iranian Foreign Ministry spokesman Esmaeil Baghaei had said Tehran’s views and observations on the US proposals would be sent after a final review.
Irna said the current phase of negotiations will focus on ending the war in the region.
Meanwhile, the US ambassador to the UN, Mike Waltz, lamented that the US was having difficulty getting in touch with Iran's supreme leader Ayatollah Mojtaba Khamenei.
Mr Waltz said that Iran’s Islamic Revolutionary Guard Corps has been largely deferential to Mr Khamenei in terms of negotiating with the US, causing everything to take longer than the US expected.
"I think part of it is that their leadership has been so devastated and so fractured, we know that the new ayatollah, the previous ayatollah's son, has been severely injured. He's in hiding and he's incredibly difficult to get a hold of," Mr Waltz told ABC.
He said it was Mr Trump's decision as to whether Iran breached a ceasefire with recent attacks against the UAE and others, and that the President decided it had not.
Also on Sunday, Israeli Prime Minister Benjamin Netanyahu told CBS that amid the continuing negotiations between the US and Iran to end the war, he would not consider the conflict ended until Iran's enriched uranium was removed.
