The ceasefire between the US and Iran is in grave peril after Iran announced on Saturday that, in response to the continued US blockade, it would once again impose travel restrictions on the Strait of Hormuz after briefly reopening it on Friday.

Iran has used the strait – through which about 20% of the world's oil passes – as a chokepoint on Western commerce in response to the war the US and Israel launched in February. It has been the linchpin of the two-week ceasefire between the two sides, which is scheduled to end Wednesday.

Tehran had announced Friday that the strait was "completely open," in response to a ceasefire between Israel and Lebanon that had taken effect. That agreement is also already falling apart following a slew of apparent violations by Israel, which has continued shelling southern Lebanon and demolishing homes even as displaced civilians return.

Iranian officials said they opted to reimpose their blockade of the strait because they believe that by continuing its own naval blockade of Iranian ports and vessels, which began over the past weekend, the US is not upholding its end of the deal.

According to a social media post from US Central Command on Saturday, the US military had already turned around at least 23 ships near the strait since its blockade began on April 13.

US President Donald Trump claimed Friday that Iran had agreed to reopen the strait without conditions, but that the US blockade would "remain in full force" until a broader deal was reached surrounding Iran's nuclear program.

But Iranian Deputy Foreign Minister Saeed Khatibzadeh said during a panel Saturday that "That is not the term we agreed on."

Iran's military headquarters later issued a formal statement declaring that it would begin limiting travel through the strait.

"The Islamic Republic of Iran, following previous agreements met in the negotiations conducted in good faith, agreed to manage the passage of a limited number of oil and commercial ships through the Strait of Hormuz," the statement said. "Unfortunately, the Americans, with their repeated breaches of trust that are part of their history, continue their acts of piracy and maritime theft under the pretext of a so-called blockade."

"This strategic waterway is under strict management and control by the armed forces," it continued. "As long as the United States does not end the complete freedom of movement for vessels from Iran to their destinations and back, the situation in the Strait of Hormuz will remain under strict control and will remain as it was before."