Washington and Tehran held historic face-to-face talks in Islamabad over the weekend, but failed to reach an immediate agreement on ending the war in the Middle East.

"Efforts are underway to bring both parties back to the table, of course we want them back in Islamabad, but the venue is not final yet," said the source, who requested anonymity due to the sensitivity of the subject matter.

"The meeting could take place soon though dates have yet to be confirmed," the source said.

The source added: "We are also working to get the ceasefire extended beyond the current deadline to allow for additional time."

A second official, who also requested anonymity, said the talks were possible before the ceasefire deadline ends next week.

"No date and venue has been decided yet," he said.

The first official said Islamabad was "the preferred venue" for Pakistan, but that nothing had yet been finalised.

"The written outlines of demands and concessions have already been shared, so both parties are aware of the potential trade-offs," the official added.

On Monday, US Vice President JD Vance said Washington had made its "red lines" clear and that "the ball is in the Iranian court."

Iran has blamed Washington for making maximalist demands, but its leaders have in the last hours not dismissed efforts by world leaders to get both sides back to the negotiating table.

A fragile two-week truce agreed last Wednesday to give time to find a lasting ceasefire remained in place, even though a US naval blockade of Iranian ports began at the Strait of Hormuz, which had been effectively closed by Tehran.