Speaking to reporters in Washington, Trump insisted that negotiations with Iran are ongoing despite Tehran's repeated denials.

He said Iran has one last chance to sign an agreement addressing the Strait of Hormuz and its nuclear weapons programme.

"We are talking right now. This is their last chance to sign a good document. I want to give them every possible opportunity before beheading," Trump said.

Trump said he agreed to continue negotiations with Iran following requests from regional countries, including Saudi Arabia, the United Arab Emirates, Qatar and others.

According to Trump, the talks should primarily focus on reopening the Strait of Hormuz, a strategic shipping route used to transport a significant share of the world's oil and other goods.

He said an agreement on the waterway could be reached "even tomorrow," but cautioned that resolving concerns over Iran's nuclear programme and eliminating its capability to develop nuclear weapons would likely take longer.

The United States and Iran have been at war since February 28, when the United States and Israel launched surprise strikes on Iran.

Despite Trump's remarks, Iran has denied that it is holding direct negotiations with Washington.

Iranian Foreign Ministry spokesperson Esmaeil Baqaei said Tehran is instead engaged in talks with Oman aimed at finding a mechanism to restore shipping through the Strait of Hormuz.

Baqaei said the two sides were close to reaching an agreement on designated shipping routes but stressed that this should not be interpreted as the full reopening of the Strait of Hormuz.