Investing.com - The U.S. military has said it has seized another oil tanker affiliated with Iran, as tensions between Washington and Tehran intensified on Thursday despite President Donald Trump’s announcement of an extended ceasefire earlier this week. The Defense Department released footage which was purported to show American troops on the deck of the vessel as it sailed in the Indian Ocean.  “We will continue global maritime enforcement to disrupt illicit networks and interdict vessels providing material support to Iran,” the Defense Department said.The news came after Iran moved to demonstrate its tightening grip on the vital Strait of Hormuz, unveiling a video which appeared to show its soldiers boarding a massive cargo ship in the area. Tehran attacked three ships in the strait on Wednesday, seizing two of them. Iranian officials said the attacks were in response to an American blockade of the country’s ports, as well as the previous U.S. seizure of an Iranian-flagged ship. A day earlier, Trump announced in a social media post that a two-week ceasefire deal with Iran had been extended just hours before it was due to expire. He said the extension came at the request of Pakistan, which has served as a mediator between Washington and Tehran, adding that the truce would be in effect "until such time as" Iranian officials present a "unified proposal" for peace.However, leaders from both sides have indicated that they stand ready to resume hostilities. In a social media post, Trump also said he had ordered the U.S. Navy to "shoot and kill any boat" that is "putting mines in the waters of the Strait of Hormuz."  "There is to be no hesitation. Additionally, our mine ’sweepers’ are clearing the Strait right now. I am hereby ordering that activity to continue, but at a tripled up level!" Trump wrote. Mediators from Pakistan, Turkey and Egypt were racing to salvage peace talks between the U.S. and Iran, including arranging a potential meeting as soon as Friday, the Wall Street Journal reported, citing officials familiar with the matter. The U.S. and Iran were exchanging messages via third parties, although little progress has been made, the WSJ said. Speaking to Fox News on Wednesday, Trump suggested that there was "no time pressure" on staging a fresh round of talks or on the ceasefire. White House Press Secretary Karoline Leavitt also said Trump does not view Iran’s ship seizures as a violation of the pause in fighting. A trip to Pakistan by U.S. Vice President JD Vance, who led a prior American delegation in talks with Tehran, has been put on hold. According to the Associated Press, Pakistani Interior Minister Mohsin Naqvi hoped for "positive progress" with Iran after meeting with U.S. Chargé d’Affaires Natalie Baker. Yet Tehran has stressed that it will not participate in any negotiations as long as the American blockade is in effect, the WSJ reported.