Iran live updates: US blockade of Iran's Strait of Hormuz ports to begin Monday

A U.S. official close to the U.S.-Iran negotiations this weekend tells ABC News that the two sides went home Saturday after failing to agree on several key issues, despite President Donald Trump's statements Sunday in a social media post that the "meeting went well" and "most points were agreed to," save for Iran's alleged refusal to abandon their nuclear ambitions.

According to the U.S. official, the key points on which Iran would not concede include ending all uranium enrichment, dismantling all major nuclear enrichment facilities and allowing the U.S. to retrieve any highly enriched uranium Iran may possess; accepting a broader peace, security and de-escalation framework that includes regional allies; ending funding for terrorist proxies Hamas, Hezbollah and the Houthis; and fully opening the Strait of Hormuz and not charging tolls for passage.

All of these points were red lines for the U.S., the official said.

-ABC News' Hannah Demissie and Justin Fishel

Iran's paramilitary Islamic Revolutionary Guard Corps (IRGC) said Sunday that any military vessels approaching the Strait of Hormuz "will be considered a violation of the ceasefire and will be met with severe force," according to Iran's semiofficial Fars news agency.

"The Islamic Revolutionary Guard Corps Navy states that, contrary to the false claims of some enemy officials, the Strait of Hormuz is under smart control and management, and remains open for the safe passage of non-military vessels in accordance with specific regulations," the statement also said.

-ABC News' Morgan Winsor and Nasser Atta

The Department of Justice will "vigorously prosecute anyone who buys or sells sanctioned Iranian oil," according to Acting Attorney General Todd Blanche.

Blanche made the announcement in a post on X Sunday afternoon, accompanied by an image of President Donald Trump's statement on social media from earlier in the day in which he announced that the U.S. Navy would blockade the Strait of Hormuz "effective immediately" after negotiations with Iran Saturday ended without an agreement to end the war.

"The Justice Department fully supports our Commander in Chief and our military," Blanche's post concluded.

Russian President Vladimir Putin held a phone call Sunday with his Iranian counterpart, President Masoud Pezeshkian, offering his support after negotiations between the U.S. and Iran failed to reach an agreement to end the conflict, despite 21 hours of trilateral talks in Pakistan.

According to the Kremlin, Putin said he was ready to mediate a settlement to the war.

"Vladimir Putin emphasized his readiness to continue to facilitate the search for a political and diplomatic settlement to the conflict and to mediate efforts to establish a just and lasting peace in the Middle East" the Kremlin said in its readout of the call.

According to Iran's semi-official news agency, Tasnim, Pezeshkian told Putin that U.S. "double standards" and a "totalitarian approach" remain the main obstacles to reaching a fair agreement in talks between Tehran and Washington.

"The Islamic Republic of Iran is fully prepared to reach a balanced and fair agreement that ensures lasting peace and security in the region. If the United States adheres to international legal frameworks, reaching an agreement is not far off," Pezeshkian said, according to Tasnim.

President Donald Trump and Vice President JD Vance have both said that Iran's alleged refusal to abandon its nuclear program is the main sticking point in the peace talks. Trump said in a Sunday post on his social media platform that "most points were agreed to" during the talks Saturday, but further said that the agreements "don't matter" if Iran is allowed to have nuclear power.

-ABC News' Claire Bower and Dragana Jovanovic