The reported visit by Field Marshal Asim Munir, a powerful figure with a growing role in Pakistan's foreign relations, comes a day after President Donald Trump warned that negotiations to end the war were on the "borderline" between a deal and renewed strikes.

A ceasefire on April 8 halted the war launched weeks earlier by the US and Israel, but negotiation efforts have so far failed to yield a lasting peace agreement.

A war of words has taken the place of open conflict but the impasse continues to weigh on the world economy, leaving everyone from investors to farmers in a painful state of uncertainty.

On Thursday, Iran's ISNA news agency said Munir's visit was aimed at continuing "talks and consultations" with Iranian authorities, without providing details. Other Iranian media carried the same report.

Pakistan hosted in April the only direct negotiations between US and Iranian officials to take place since February 28, the day the war began.

Munir was at the centre of the action during that round of talks, greeting both delegations on their arrival and displaying remarkable bonhomie with US Vice President JD Vance.

But the talks ultimately failed, with Iran accusing the US of making "excessive demands".

Since then, the two sides have sent to each other multiple proposals, with the threat of renewed war looming all along.

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

He said a deal could come "very quickly" or "in a few days", but warned Tehran would have to provide "100 percent good answers".

- 'Forceful response' -

Tehran's chief negotiator Mohammad Bagher Ghalibaf on Wednesday accused Washington of seeking to restart the war, while warning of a "forceful response" if Iran is attacked.

"The enemy's movements, both overt and clandestine, show that despite economic and political pressure, it has not abandoned its military objectives and is seeking to start a new war," Ghalibaf said.

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

Trump is under political pressure at home as energy costs rise.

The ceasefire halted the fighting but has not reopened the Strait of Hormuz, the vital waterway that normally carries about a fifth of the world's oil and liquefied natural gas.

The future of Hormuz remains a key sticking point in the negotiations, with fears growing that the global economy will feel more pain as pre-war oil stockpiles run down.

Iran imposed the blockade of Hormuz as part of its retaliation in the war, allowing only a trickle of vessels through in recent weeks while introducing a toll system.

Hormuz also carries around a third of global fertiliser shipments, raising concerns of higher food prices and shortages if the closure drags on.

The UN Food and Agriculture Organisation said the closure could trigger "a severe global food price crisis" and a "systemic agrifood shock".

Cautious hope rippled through financial markets on Thursday, with crude prices edging up around 0.5 percent. On Wednesday oil had fallen more than five percent, while US stocks rose.

Analysts warned that investors remained wary after weeks of false starts in the negotiations.