Iran has threatened to escalate military tensions in the Strait of Hormuz and across the region if diplomacy with the United States fails, as a 60-day negotiating period set out in a June memorandum expired without a permanent agreement.

A senior Iranian official told Reuters on Monday that Tehran had decided to shift its policy from defensive to “fully offensive” because of the deadlock in efforts to secure a lasting end to the war.

“Iranian entities must be prepared to escalate tensions in the Strait of Hormuz and wider region,” the official said, adding that Iran would be prepared to carry out a “timely and precise” military attack aimed at breaking the US naval blockade if diplomatic efforts failed.

The warning came on the day Washington and Tehran had been expected to reach a final agreement under a memorandum of understanding signed on 17 June.

The document set out a 60-day period, extendable by mutual agreement, for negotiations intended to address wider disputes, including Iran’s nuclear programme. The arrangement quickly unravelled as the two sides accused each other of violations and clashed over control and navigation through the Strait of Hormuz.

Iranian Foreign Ministry spokesman Esmaeil Baghaei disputed the description of Monday as a fixed deadline.

“There is no provision in the memorandum of understanding referring to a ‘60-day deadline’, and the Islamic Republic of Iran never formulates its policies under pressure, ultimatums or time limits,” Baghaei told reporters in Tehran.

He said the memorandum instead provided for 60 days of negotiations on sanctions relief and the nuclear issue, with the possibility of extending the period.

Baghaei said the timetable had “completely lost its relevance” because, according to Tehran, Washington had committed “flagrant and widespread” violations of the memorandum before negotiations could begin. The United States and Iran have each accused the other of breaching the June arrangement.

President Donald Trump reiterated on Monday that preventing Iran from obtaining a nuclear weapon remained Washington’s central objective.

“The number one Goal is, and always will be, that Iran cannot have, in any way, shape, or form, a Nuclear Weapon,” Trump wrote on Truth Social.

Trump also told Fox News that he had no timetable for ending the conflict, saying: “I don’t have a timeline. I’m in no hurry.”

The June memorandum called for an end to military operations and was intended to establish a path towards reopening the Strait of Hormuz and settling the nuclear dispute. But hostilities resumed after disagreements over the waterway, which connects Gulf energy producers with international markets.

Shipping through the strait has again fallen to a fraction of its pre-war level. Kpler tracking data cited by Reuters showed five commodity vessels passing through on Saturday and none on Sunday, although ships travelling with their tracking systems switched off may not appear in the figures.

Before the war began on 28 February, more than 130 ships crossed the strait each day, according to Reuters. The waterway handled roughly one-fifth of global crude oil and liquefied natural gas shipments.

The latest slowdown followed attacks last week on three tankers operated by the Abu Dhabi National Oil Company, according to the United Arab Emirates.

Talks over the strait have continued separately between Iran and Oman. Baghaei said on Monday that work on a maritime transit arrangement was continuing, describing negotiations as complicated by security conditions and the number of parties involved.

Pakistan has also sought to keep diplomatic efforts alive. Pakistani Foreign Ministry spokesman Tahir Andrabi said last week that Islamabad was making “all-out efforts” to return Washington and Tehran to negotiations.

The senior Iranian official who spoke to Reuters said Tehran would now set its own period of “a few weeks” for the United States to implement provisions of the June agreement, with mediators expected to communicate that position to Washington and other governments in the region.

No permanent agreement had been announced by Monday evening.