Iran live updates: Trump says US Navy attacked and seized Iranian-flagged cargo ship

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

Iran's parliament speaker and chief peace negotiator, Mohammad Bagher Ghalibaf, said talks with the United States have made progress, but "many gaps and some fundamental points remain."

Speaking on Iranian state TV in a long address that ran for about an hour, covering the recent talks in Islamabad, Ghalibaf said the two sides had reached agreement on some matters, while others remain unresolved, with new proposals still under discussion.

He said both sides have "one or two" core issues that are non-negotiable, adding that "the distance to a final agreement remains considerable."

Ghalibaf stressed that the United States must take steps to build trust with the Iranian public, calling it "the most important step" in the process.

-ABC News’ Rashid Haddou and Maryam Rahimi