President Donald Trump said in a post on his social media platform Sunday afternoon that the U.S. Navy had attacked an Iranian-flagged cargo ship in the Gulf of Oman and that U.S. Marines have taken custody of the vessel.

“Today, an Iranian-flagged cargo ship named TOUSKA, nearly 900 feet long and weighing almost as much as an aircraft carrier, tried to get past our Naval Blockade, and it did not go well for them,” Trump said in the post.

U.S. Central Command confirmed that the destroyer USS Spruance intercepted the Touska as it transited the North Arabian Sea towards the Iranian port of Bandar Abbas. 

After repeated warnings over a six-hour timespan, the destroyer warned the Touska’s crew to vacate the engine room and fired several rounds at that location from its five-inch gun, according to CENTCOM.

Marines later boarded the ship, and it remains in U.S. custody, CENTCOM said.

It appears to be the first instance of the U.S. attacking and seizing a merchant vessel since it instituted the blockade of Iranian ports.

The president further wrote that "U.S. Marines have custody of the vessel," which he said is "under U.S. Treasury Sanctions because of their prior history of illegal activity. We have full custody of the ship, and are seeing what’s on board!"

The move comes after Joint Chiefs Chairman Gen. Dan Caine warned that the U.S. would actively enforce the blockade on Iranian-flagged vessels around the globe.

"In addition to this blockade, the joint force, through operations and activities in other areas of responsibility, like the Pacific area of responsibility under the command of Admiral Paparo, will actively pursue any Iranian-flagged vessel or any vessel attempting to provide material support to Iran. This includes Dark Fleet vessels carrying Iranian oil," Caine said in a Pentagon press conference Thursday.

-ABC News' Nicholas Kerr

As Tehran asserts that it will not participate in a second round of in-person talks with U.S. negotiators in Islamabad, Pakistan, on Monday unless the naval blockade on Iranian ports is lifted, President Donald Trump is claiming that a peace deal is almost complete.

"I feel fine about it. The concept of the deal is done. I think we have a very good chance to get it completed," Trump told Axios in an interview on Sunday.

The president offered no details regarding what was in the deal.

Trump's comments to Axios were published just hours after he threatened to bomb all of Iran's power plants and bridges if the Iranians don't sign the deal.

“If the deal isn’t done, the deal that we made, then I’m going to take out their bridges and their power plants," Trump told Fox News in a separate interview. “If they don’t sign this thing, the whole country is going to get blown up.”

The president told ABC News' Jonathan Karl something similar Sunday.

"It’s going to be very good," Trump said. "They are either going to do it or they are going to have problems. We’ll see what happens."

The present ceasefire agreement is set to expire on Wednesday.

-ABC News' Nicholas Kerr

President Donald Trump said Sunday morning that the entire country of Iran would get “blown up” if leaders there don’t sign a deal with the U.S.

"If they don't sign this deal, the whole country is going to get blown up," Trump told Fox News, shortly after he wrote on his social media platform that talks would resume in Islamabad on Monday.

The president later told The New York Post that his advisers, special envoy Steve Witkoff and Jared Kushner, would be heading to Islamabad on his behalf.

The president did leave open the possibility that he could travel to Islamabad at some point, but gave no indication when.

“I would say maybe at a little bit later date. We have to see how it works out tomorrow,” he said.

-ABC News' Nicholas Kerr

President Donald Trump said in a Sunday post on his social media platform that he was dispatching his representatives to Islamabad, Pakistan, for another round of peace talks with Iran on Monday night.

"My Representatives are going to Islamabad, Pakistan – They will be there tomorrow evening, for Negotiations," the president wrote.

He also blasted Iran for allegedly firing on vessels transiting the Strait of Hormuz Saturday, which he called a “total violation” of the ceasefire, and urged Iran to make a deal with the U.S. or face strikes on power plants and bridges inside the country.

“We’re offering a very fair and reasonable DEAL, and I hope they take it because, if they don’t, the United States is going to knock out every single Power Plant, and every single Bridge, in Iran. NO MORE MR. NICE GUY!" Trump wrote. "They’ll come down fast, they’ll come down easy and, if they don’t take the DEAL, it will be my Honor to do what has to be done, which should have been done to Iran, by other Presidents, for the last 47 years. IT’S TIME FOR THE IRAN KILLING MACHINE TO END!"

Trump made a similar threat against Iran on Easter weekend, posting on his social media platform that he would bomb Iran's power plants and bridges and send the country "back to the Stone Ages, where they belong" if they didn't then open the Strait of Hormuz to shipping traffic.

The current ceasefire agreement is set to expire on Wednesday.

-ABC News' Nicholas Kerr

The current Iranian negotiations leader, Mohammed Ghalibaf, the speaker of the Iranian Parliament, posted a statement to social media Friday evening stating President Donald Trump "made seven claims in one hour, all seven of which are false."

Ghalibaf's statement also echoes what Foreign Ministry spokesperson Esmael Baqaei said earlier -- that Iran would not allow navigation in the Strait of Hormuz if the American blockade continued, and that navigation will be carried out based on a "designated route" and with "Iranian permission."

He added that the "open or closed status of the Strait and the regulations governing it will be determined by the field, not social media."

The statement went on to say: "Media warfare and public opinion engineering are an important part of the war, and the Iranian nation will not be affected by these tricks."

-ABC News' Victoria Beaule