President Donald Trump has warned that any future U.S. attack on Iran could be “much worse” than previous actions unless Tehran reaches an immediate agreement with Washington.

In a post on social media, Trump said he was prepared to carry out missions “with speed and risk” if necessary, referencing the recent deployment of the aircraft carrier USS Abraham Lincoln and accompanying warships to the Gulf.

Trump, who has previously taken action against Venezuela, said Iran is running out of time and urged the country to “come to the negotiating table” over its nuclear program. He added that U.S. efforts to initiate talks have so far gone unheeded, referring to a June airstrike: “I told them to come to negotiations and reach an agreement, but they didn’t come.”

Iran’s Foreign Minister told state media that no formal negotiations have been launched, though contacts with neighbouring countries have begun.

The president’s comments follow the arrival in the Middle East last week of the USS Abraham Lincoln and several other warships, signalling heightened U.S. military readiness in the region.