U.S. President Trump [AP Yonhap News]

The U.S. military, which has been conducting a maritime blockade operation against Iran, fired on and seized an Iranian cargo ship two days before the end of a two-week ceasefire on the 19th (local time).

As Iran retaliates, demanding the lifting of the maritime blockade against it, in response to President Trump's claim that negotiations would take place on the 20th, the U.S. military's firing on and seizing of an Iranian vessel is expected to become a significant variable in resuming negotiations.

Iran has announced retaliation.

President Trump announced on the social media platform Truth Social, "Today, an Iranian cargo ship named 'Tusca,' approximately 900 feet long (about 275 meters) and weighing as much as an aircraft carrier, attempted to break through our maritime blockade and was unsuccessful."

He added, "The U.S. Navy guided-missile destroyer USS Spruance issued a lawful warning to the Tusca in the Gulf of Oman to stop, but the Iranian crew did not comply, and our naval warship disabled it by puncturing its engine room."

He continued, "The U.S. Marines are currently on board that vessel, and we are looking at what's inside," adding that the Iranian cargo ship was on the U.S. Treasury Department's sanctions list due to its history of illegal activities.

Shortly thereafter, U.S. Central Command announced the specific details of the incident.

The Tusca, en route to Bandar Abbas in southern Iran at a speed of 17 knots, was warned that it was violating the U.S. blockade but did not comply for six hours. After the U.S. military ordered an evacuation of the engine room, they fired multiple rounds from a 5-inch (127 mm) MK45 naval gun to disable its propulsion system.

Following this, the 31st Marine Expeditionary Unit boarded the Tusca, and the vessel is currently detained, Central Command explained. It appears that the 31st MEU, which was stationed in Japan, was deployed to the Middle East and involved in the maritime blockade operation against Iran.

Central Command stated that the U.S. military acted in a prudent, professional, and proportionate manner, adding that since the commencement of the maritime blockade against Iran, they have directed 25 merchant vessels to turn back or return to Iranian ports.

It is believed that President Trump ordered this operation to maximize pressure on Iran as the "two-week ceasefire" nears its end on the 21st. It can also be interpreted as a response to Iran's military forces re-blocking the Strait of Hormuz and attacking vessels.

The U.S. had previously turned back about 20 Iranian vessels attempting to sail through the U.S. blockade after departing from Iranian ports, but this is the first time that the use of force has been reported, according to the U.S. daily Wall Street Journal (WSJ).

However, at the crossroads of negotiation or escalation, Iran's response based on the alleged violation of the ceasefire agreement will be a crucial variable in determining whether negotiations will resume.

A spokesperson for the central military headquarters of Hatam al-Anbiya, which commands the Iranian military, stated through state media that the U.S. military's firing was a violation of the ceasefire agreement and that they would respond and retaliate soon. Specific response measures were not disclosed.

Attention is focused on whether a negotiation table can be arranged between the U.S. and Iran before the two-week ceasefire ends, as President Trump has resorted to force against Iran, which demanded the lifting of the maritime blockade, by attacking and seizing an Iranian merchant ship.

If Iran, prioritizing negotiations, moderates its retaliatory measures, negotiations that broke down on the 11th could potentially resume as early as the 20th. However, the possibility of the already precarious negotiation momentum being shattered amid heightened military tensions cannot be ruled out.

President Trump announced via Truth Social on the morning of the 19th that the U.S. negotiation delegation to Iran was heading to Islamabad, Pakistan, and that negotiations would take place on the evening of the 20th, threatening to bomb all power plants and bridges if Iran did not accept the agreement.

In an interview with the online U.S. media Axios on the same day, President Trump expressed optimism about the outcome of the negotiations.

He said, "I feel good about it. The basic framework for an agreement has been established. I see a very high probability of completing (a deal)."

In line with the ceasefire agreement with Israel and Lebanon, Iran had reopened the Strait of Hormuz, but after just one day, Iran's military forces re-imposed the blockade, citing the continuation of the U.S. maritime blockade against Iran as an issue.