Iran has launched major naval exercises in the Persian Gulf just days before the United States is due to start reimposing sanctions on Tehran, according to media reports citing U.S. officials.
One U.S. official told Reuters on August 2 that possibly more than 100 vessels are involved in the drills, in a move that appears designed to send a message to Washington.
A U.S. official told AFP that the vessels are mostly small attack boats and that there have been no interactions with U.S. ships in the area thus far.
The timing of the drills is unusual, as Iran's navy usually conducts annual exercises in the autumn, the officials said.
Tensions between Washington and Tehran have escalated since U.S. President Donald Trump announced in May that he was pulling out of Iran's nuclear deal with world powers and reimposing sanctions on Tehran.
The first batch of renewed U.S. sanctions is due to go into effect on August 7.
The looming threat of sanctions is already putting significant pressure on the Iranian economy. Iran's currency fell to new record lows this week, helping to spark street protests in several Iranian cities.
Hundreds of people were reported rallying in Tehran, Isfahan, Karaj, Shiraz, Mashhad, and Ahvaz to protest high inflation caused in part by the weak rial.
The plummeting currency, which leads to higher prices for imported goods, has been fueling sporadic protests since the beginning of the year. Some protests also have focused on water shortages, power cuts, and alleged corruption in the government.
With tensions rising, U.S. and Iranian forces in the Persian Gulf have also gone on heightened alert. Washington has made clear that the sanctions are aimed at choking off Iran's oil exports, which are an important driver of the country's economic growth and must flow through the Gulf to reach global markets.
The United States has not threatened to use military means to cut off Iran's oil exports, but it has ratcheted up financial sanctions and put pressure on Iran's global customers in Europe and Asia to stop importing its oil.
Senior Iranian officials have warned that they will fight the U.S. efforts to cut off the country's oil exports.
Iran's Islamic Revolutionary Guards Corps has warned that it might retaliate against any attempt to block Iranian oil exports by blocking the Strait of Hormuz, a strategic artery not only for Iran's exports but for the oil exports of other Persian Gulf nations like Kuwait and Iraq.
The U.S. military's Central Command said on August 1 that it has seen an increase in Iranian naval activity, including in the Strait of Hormuz.
"We are monitoring it closely and will continue to work with our partners to ensure freedom of navigation and free flow of commerce in international waterways," said Navy Captain Bill Urban, the chief spokesman at Central Command, which oversees U.S. forces in the Middle East.
U.S. officials told the media that the increased Iranian naval operations in the Gulf to date have not affected commercial maritime activity.
Iranian authorities have not commented on the increased activity detected by the Pentagon.