US Vice President JD Vance said on Tuesday that Washington remains confident it will still receive a response from Iran before President Donald Trump's deadline expires, despite no signs that Iranian leaders are prepared to compromise.

"Iranians have not been the fastest negotiators and they still are not," Vance said during a visit to Budapest.

Echoing Trump's earlier remarks, Vance said the US has largely accomplished military objectives in the Iran war.

Meanwhile in Washington, Trump escalated his rhetoric, warning that "a whole civilization will die tonight" if Iran fails to meet his deadline to reach a deal and reopen the Strait of Hormuz.

Iran, however, has struck a defiant tone, with reports saying Tehran had rejected a US proposal for an immediate ceasefire, while the Islamic Revolutionary Guard Corps warned of a response that would "go beyond the region."

Global markets are watching closely for signs of de-escalation ahead of Trump's deadline. Reports suggest that diplomatic efforts led by Pakistan are still underway.