Trump says US Navy attacked and seized Iranian-flagged cargo ship

President Donald Trump on Sunday night lashed out against Pope Leo XIV on social media, calling the first-ever American pontiff “weak” over his calls for the U.S. war in Iran to end.

“Pope Leo is WEAK on Crime, and terrible for Foreign Policy,” Trump wrote on social media. The president added, “I don’t want a Pope who thinks it’s OK for Iran to have a Nuclear Weapon.”

In recent weeks, the Pope has criticized the war in Iran and called for peace in the Middle East.

Earlier this month, the Pope asked “all people of goodwill to search always for peace and not violence, to reject war, especially a war which many people have said is an unjust war, which is continuing to escalate and which is not resolving anything.”

And on Saturday, the Pope referred to the U.S. military offensive in Iran as a “delusion of omnipotence,” imploring the country leaders to come to a peace agreement.

-ABC News' Fritz Farrow and Emily Chang

U.S. forces will begin a blockade of maritime traffic to and from Iranian ports Monday morning, according to U.S. Central Command.

"U.S. Central Command (CENTCOM) forces will begin implementing a blockade of all maritime traffic entering and exiting Iranian ports on April 13 at 10 a.m. ET, in accordance with the President’s proclamation," according to a CENTCOM statement late Sunday afternoon.

"The blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman," the statement continued, adding that CENTCOM forces "will not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports."

President Donald Trump said Sunday morning in a post on his social media platform that the U.S. will "immediately" begin a blockade of the Strait of Hormuz, following the failure of peace negotiations between the U.S. and Iran.

Commercial mariners will be provided with additional information prior to the start of the blockade, according to CENTCOM, which also advised "all mariners" to monitor advisory broadcasts and contact U.S. naval forces "when operating in the Gulf of Oman and Strait of Hormuz approaches."

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