The United States and Iran said Monday they had again traded strikes, straining an already fragile ceasefire as negotiations between the two sides have stalled.

Weeks of complicated talks marked by sharp rhetoric and occasional flare-ups of violence have not managed to reach a deal to end the war and reopen the Strait of Hormuz, which is essential to oil supplies.

Iran's chief negotiator warned the United States is not to be trusted Sunday, saying Tehran would not agree to any deal with Washington unless it fully secures Iranian rights.

U.S. President Donald Trump said he had secured guarantees from Iran that it would not develop nuclear weapons, as reports emerged he had sent a tougher peace proposal back to Tehran.

Any tweaks to the proposal could prolong even further an agreement to formally end the Middle East war and open the Strait of Hormuz maritime route after weeks of efforts to secure a deal despite fractious rhetoric and the occasional flare up of armed conflict.

The United States warned on Saturday it was "more than capable" of resuming war with Iran after President Donald Trump said any peace deal must adhere to his red lines, including Tehran never being able to develop nuclear weapons.

U.S. President Donald Trump on Friday said he was now making a "final" decision on whether or not to strike a peace deal with Iran.

U.S. President Donald Trump said any agreement with Iran would depend on securing a “good deal” for the United States as negotiations over Tehran’s nuclear program intensify alongside continued military tensions in the Gulf.

“A deal that wasn’t going to be good for us is the line,” Trump told Fox News in an interview set to air this weekend. “I negotiate. They negotiate. They’re very good negotiators.”

The United States and Iran have made good progress towards a ceasefire extension deal but President Donald Trump is not yet ready to approve it, U.S. Vice President JD Vance said Thursday.

U.S. and Iranian negotiators have reached an agreement on a 60-day memorandum of understanding to extend the ceasefire and launch negotiations on Iran's nuclear program, but U.S. President Donald Trump has yet to give it his final approval, two U.S. officials and a regional source involved in the mediation efforts told U.S. news portal Axios.

U.S. President Donald Trump said Wednesday he was not yet satisfied with Iran's offers to make a deal, after Iranian state television reported details of what it claimed was a draft agreement.

U.S. President Donald Trump on Wednesday appeared to threaten to attack U.S. ally Oman if it sides with Iran over reopening the Strait of Hormuz.

Trump said Oman must "behave" or he would "blow them up," when he was asked if he would accept a short-term deal to allow Iran and the Gulf state to control the waterway.