The US will not lift its blockade on Iranian ports until a deal has been reached with Tehran, US President Donald Trump has said, amid continuing uncertainty over whether fresh talks to end the war will take place.

The blockade, which began a week ago, is "absolutely destroying Iran", Trump wrote on his social media platform Truth Social, adding his country was winning the conflict "by a lot".

His comments come with the temporary US-Iran ceasefire set to end on Wednesday, but with no certainty over whether a second round of peace talks will go ahead in Pakistan.

There is tightened security in Pakistan's capital in anticipation of a meeting. But US Vice President JD Vance - set to lead the US delegation - has not yet left Washington, while Iran says it has not decided whether to attend.

Since the blockade began, US forces have directed 27 vessels to turn around or return to an Iranian port, according to US Central Command (Centcom).

The US also intercepted and seized an Iranian-flagged cargo ship for the first time in the conflict, after it tried to get through the blockade on Sunday.

Iran said it would keep the route shut until the US stopped the blockade of its ports.

There are indications a second round of peace talks between the US and Iran will go ahead, despite Tehran refusing to confirm whether it will send a delegation.