Iran's ISNA news agency said Munir's visit was aimed at continuing "talks and consultations" with Iranian authorities, but did not provide details. Other Iranian media carried the same report.

Munir's visit comes after Pakistan's Interior Minister Mohsin Naqvi travelled to Iran on Wednesday and met President Masoud Pezeshkian and Foreign Minister Abbas Araghchi.

Pakistan, Iran's eastern neighbour, has been mediating between Tehran and Washington in an effort to end the war, which broke out on February 28 when the US and Israel launched attacks.

A ceasefire agreement since April 8 has halted hostilities but US President Donald Trump warned on Wednesday that the window for diplomacy was closing.

"It's right on the borderline, believe me," Trump told reporters. "If we don't get the right answers, it goes very quickly. We're all ready to go."

Tehran's chief negotiator Mohammad Bagher Ghalibaf on Wednesday accused Washington of seeking to restart the war after Trump threatened renewed attacks.

Ghalibaf warned of a "forceful response" from Iran, while the country's Revolutionary Guards said any renewed conflict would spread far beyond the Middle East.

Iranian foreign ministry spokesman Esmaeil Baqaei said Wednesday that Tehran was examining points received from Washington, while repeating Iran's demands for the release of its assets frozen abroad and an end to a US naval blockade of Iranian ports.