Iran’s chief negotiator said Tuesday that Washington must accept Tehran’s latest peace plan or face failure, after US President Donald Trump warned the truce in the Middle East war was on the brink of collapse.

The war, which erupted more than two months ago with US-Israeli strikes on Iran, has spread throughout the Middle East and roiled the global economy despite the ceasefire, impacting hundreds of millions worldwide.

Both sides have refused to make concessions and repeatedly threatened to resume fighting, but neither appears willing to return to all-out war.

“There is no alternative but to accept the rights of the Iranian people as laid out in the 14-point proposal. Any other approach will be completely inconclusive; nothing but one failure after another,” Mohammad Bagher Ghalibaf said in a post on X.

“The longer they drag their feet, the more American taxpayers will pay for it.”

The Pentagon said on Tuesday that the cost of the war had climbed to nearly $29 billion – about $4 billion higher than an estimate offered two weeks ago.

Iran sent its latest proposal in response to an earlier US plan, details of which remain limited. Media reports have said the American plan involved a one-page memorandum of understanding aimed at ending the fighting and establishing a framework for negotiations on Iran’s nuclear programme.

Iran’s foreign ministry said its response called for ending the war on all fronts, including in Lebanon, halting the US naval blockade of Iranian ports and securing the release of Iranian assets frozen abroad under longstanding sanctions.

But Trump slammed Tehran’s reply as “TOTALLY UNACCEPTABLE”, saying the United States would enjoy a “complete victory” over Iran and that the truce that has halted fighting for over a month was on its last legs.

The US president subsequently said ahead of his Tuesday departure for a trip to China that he would have a “long talk” with counterpart Xi Jinping about Iran, but that he does not need Beijing’s help to end the war.

In a show of defiance, Iran’s Revolutionary Guards said they carried out drills in Tehran aimed at “enhancing combat capability to confront any movement of the American-Zionist enemy”, state media reported Tuesday.

Defence Ministry spokesman Reza Talaei-Nik said that if the US “does not submit to the rightful and definitive demands of the Iranian nation in the diplomatic arena, it should expect a repeat of its defeats on the military battlefield”.