The US and Iran have been in indirect talks aimed at extending the two-week ceasefire beyond its expiry on 22 April, as Pakistan’s army chief arrived in Tehran to continue mediation efforts.

Karoline Leavitt, the White House press secretary, denied on Wednesday that the US had “formally” requested to extend the two-week ceasefire but added that Washington remained “very much engaged in these negotiations”.

A second round of negotiations would “very likely” be held in Islamabad, she said, adding that the White House feels “good about the prospects of a deal” only days after negotiations to reach a peace agreement failed.

Nothing is official until you hear it from us here at the White House,” she added.

The remarks came as Pakistani officials launched a new round of shuttle diplomacy in an effort to negotiate an end to the conflict, travelling to Iran and other countries in the region to marshal diplomatic support for a peace agreement.

Sources in Tehran said Iran demanded an end to Israeli attacks on Lebanon as a precondition for another round of negotiations with the US. Israel has portrayed its talks with the Lebanese government in Washington as a “historic opportunity” to end the Iranian-allied Hezbollah militia’s grip on Lebanon.