The temporary ceasefire between the United States and Iran entered its seventh day on Monday, as Iran threatened retaliatory measures against Gulf ports while the US military began a blockade of Iranian ports.

Oil prices climbed back above $100 per barrel, with no immediate sign of a swift reopening of the Strait of Hormuz to ease the unprecedented disruption in supply. Concerns over the durability of the two-week ceasefire, reached last week, have intensified, particularly after weekend talks in Islamabad between the US and Iran yielded no results.

The latest tit-for-tat threats over port operations have cast doubt on the 14-day ceasefire, raising fears that it could unravel.

Ceasefire under strain

The US Central Command stated that the blockade would be "enforced impartially against vessels of all nations" entering or leaving Iranian ports in the Gulf and the Gulf of Oman. "The blockade will not impede neutral transit passage through the Strait of Hormuz to or from non-Iranian destinations," the command added in a note to seafarers obtained by Reuters.

An Iranian military spokesperson denounced any US restrictions on international shipping as "piracy," warning that if Iranian ports were threatened, no port in the Gulf or Gulf of Oman would be secure. The Islamic Revolutionary Guards Corps (IRGC) further stated that any military vessels approaching the strait would violate the ceasefire.

The IRGC also vowed to deploy new military capabilities if hostilities with the US and Israel continue, according to the semi-official Fars News Agency. "We have not yet used our capabilities, and if the war continues, we will unveil capabilities that the enemy has no idea about," IRGC spokesperson Hossein Mohebbi said.

Meanwhile, Iran's UN delegation requested reparations from Saudi Arabia, the UAE, Bahrain, Qatar and Jordan, alleging that their territories were used to support US-Israeli actions against Iran.

Military commentator Wei Dongxu told CMG that the US blockade has two objectives: demonstrating coercive capability during a ceasefire by disrupting Iran's maritime lines of communication, and potentially preparing for future military operations amid ongoing US military buildup. Wei cautioned that in the event of conflict, the blockade could destabilize the fragile ceasefire and trigger a new round of hostilities, while disrupting international shipping and complicating energy and goods transport.

Read more: 

Explainer: US blockade of Strait of Hormuz – sustainability and consequences

Possible next US-Iran talks

US President Donald Trump said Monday that his administration received a call from Tehran, indicating that Iran "would like to make a deal very badly," signaling a mutual interest in resolving the conflict. He emphasized that nuclear issues remain the primary sticking point, particularly regarding the retrieval of Iran's enriched uranium.

Washington has proposed a 20-year suspension of Iran's nuclear program, while Iran offered a suspension of up to five years during stalled talks in Pakistan over the weekend, according to The New York Times. 

The United States and Iran are still engaged in talks as the two sides work toward a diplomatic off-ramp for the war, a US official told CNN on Monday.

Mediators from Pakistan, Egypt and Türkiye are working to revive negotiations between the United States and Iran before the current ceasefire expires, according to reports.

UN Secretary-General Antonio Guterres calls on US-Iranian negotiations to continue constructively for an agreement to be reached, said his spokesman on Monday. 

A regional source told Axios, "We are not in a complete deadlock. The door is not closed yet. Both sides are bargaining. It's a bazaar." 

Pakistani Prime Minister Shehbaz Sharif also indicated that efforts to resolve the conflict are ongoing. Two Pakistani officials told AP that Pakistan proposed to hold a second round of talks between Iran and America in Islamabad. Meanwhile, US officials told AP that the second round of negotiations between America and Iran may be held Thursday.

Hezbollah rejects Israel talks, vows continued resistance

Separately, Israel continued its military operations in Lebanon. On Monday, Israeli troops targeted a key town in southern Lebanon reportedly controlled by Iran-backed Hezbollah. Israel and the US have maintained that the campaign is not part of the ceasefire, while Iran insists otherwise.

Hezbollah leader Naim Qassem declared on Monday that the militant group rejects direct talks with Israel and will continue its "resistance" as ambassadors from Lebanon and Israel prepared for talks in Washington on Tuesday.

"We will stay on the battlefield until our last breath," Qassem said in a televised speech on al-Manar TV.

Qassem said the "US-backed Israeli aggression" was against Lebanon as a whole, not only Hezbollah. He called on Lebanese authorities to enforce existing agreements, including an Israeli withdrawal, the return of displaced civilians, reconstruction efforts and the release of detainees.

Qassem rejected current diplomatic initiatives, saying proposed negotiations with Israel amount to "submission and surrender" and lack national consensus. He warned that such talks, as described by Israeli officials, aim to disarm Hezbollah and normalize relations with Israel.

(With input from agencies)