The two-week ceasefire between Iran and the United States is under mounting pressure.

After high-level negotiations between the two countries broke down on Saturday, President Donald Trump announced a blockade of ships of all nations leaving Iranian ports effective today.

The Iranian regime responded with a threat to retaliate against oil tankers and other commercial ships leaving the Gulf Arab countries and said any military vessel approaching the Strait of Hormuz would be considered to have violated the ceasefire.

The upshot is that no commercial vessels are likely to risk defying Iran’s current chokehold on the Strait, the narrow waterway at the mouth of the Gulf through which some 20 percent of global oil supplies normally pass along with other important commodities.

Making matters worse, the US Navy and maritime forces of Iran’s Islamic Revolutionary Guard Corps (IRGC) now may be on a collision course.

The negotiations in Pakistan on Saturday between a US delegation led by Vice President JD Vance and an Iranian delegation led by Mohammad Bagher Ghalibaf, one of the most powerful surviving figures in the regime, ended after 21 hours.  Vance said there were “substantive discussions” but that the US was unwilling to back off its “red lines,” particularly allowing Iran the ability to develop nuclear bombs.

Neither side committed to another round of negotiations, although talks may be taking place behind the scenes and another meeting is possible.

The problem is that the Shia fundamentalist Iranian regime is apocalyptic in nature and following six weeks of intensive US and Israeli bombing of its military assets and leadership regards itself as waging an existential war.

It is more unlikely than ever to scrap its nuclear program and likely believes that soaring gasoline prices in the US have put Trump on the defensive.

The bottom line is that full-scale war could re-erupt and that if it does not Iran and the US could remain locked in a dangerous standoff for weeks or even months to come.

For the time being, relative calm has returned to the Gulf Arab countries, which have suffered no Iranian missile or drone attacks since the initial hours after the truce was announced last Wednesday.

Most airlines from outside the region probably will not resume flights without certainty that the two-week truce will hold and be extended.

The Gulf Arab countries routinely are arresting people, including Westerners, who share cell phone videos of or social media posts about local military assets and Iranian missile and drone impacts. 

Israel has not come under Iranian missile attack since early Wednesday but that could change at any time.  The Israeli military continues to stage heavy airstrikes and press ahead with a ground offensive in Lebanon against Iranian proxy Hizbollah, which continues to fire rockets and drones at northern Israel and to a lesser extent central Israel.