By The South Asia Times

ISLAMABAD – The Pakistani capital was placed under virtual lockdown on Sunday as US and Iranian officials began arriving for a second round of talks aimed at finalizing a potential breakthrough agreement, with authorities sealing the city's heavily fortified Red Zone and banning heavy vehicle movement until further notice.

Islamabad police issued a traffic advisory sealing the Red Zone — home to key diplomatic missions, government buildings, and the Serena Hotel -- from Sunday onward. The Information Ministry has also commenced registration of journalists to cover the high-profile event, while security forces have sealed the premises of the Serena Hotel, where the first round of US-Iran talks was held and where US Vice President, Iran's Speaker of Parliament, and foreign ministers previously stayed.

In a sign of serious logistical preparations, a US Air Force C-17 cargo aircraft reportedly landed at Nur Khan Airbase in Rawalpindi on Sunday, carrying armored vehicles, trucks, and pallets of equipment, according to sources. The cargo is believed to be the logistics backbone for the high-level meeting at the Serena Hotel in Islamabad; however, Pakistani officials didn't confirm the arrival.

- Trump Spoke with Pakistan's Army Chief, Axios Reports

According to US media reports, President Donald Trump personally spoke with Pakistani Army Chief Field Marshal Asim Munir as well as Iranian negotiators this week. The Axios outlet, citing unnamed US officials, reported that the calls came during Munir's three-day trip to Tehran, which began Wednesday.

"Pakistani army chief Asim Munir held mediation talks between the US and Iran in Tehran this week, and US officials said Trump spoke by phone at least once with Munir and the Iranians," Axios reported.

During his Tehran visit, Munir met with both civil and military leaders, including Parliament Speaker Mohammad Bagher Qalibaf, Foreign Minister Abbas Araghchi, and Major General Ali Abdollahi, commander of the Khatam ul Anbiya headquarters.

Pakistan's Deputy Prime Minister and Foreign Minister Ishaq Dar also spoke with his Iranian counterpart on Sunday, discussing delegation arrivals and the potential agreement between the US and Iran, diplomatic sources confirmed.

Sources familiar with the negotiations said the majority of points presented by both sides during the first round have already been agreed upon, while discussions continue on a handful of remaining issues. This round is considered critically important, with sources suggesting both sides may sign a Memorandum of Understanding (MOU) during the Islamabad talks, followed by a formal agreement within 60 days.

Another source indicated that Munir's three-day diplomatic push in Tehran resolved "majority of the outstanding issues," paving the way for a possible breakthrough.

- Technical Teams to Meet Monday

Technical teams from the US and Iran are expected to meet on Monday in Islamabad to prepare signing documents for high-level officials. One source said the formal signing could take place on April 21, though no official confirmation has been provided by any of the parties involved.

With the Red Zone sealed and security at maximum, Islamabad resembles a city awaiting history. No official statement has been issued by the US or Iranian governments confirming their delegations' arrival, but the logistical footprint -- armored vehicles, sealed hotels, and grounded cargo planes -- tells its own story.

The world now watches as Pakistan, a nation with unique ties to both Washington and Tehran, prepares to host what could be one of the most consequential diplomatic breakthroughs in decades.