Iran began a large-scale exercise in the Strait of Hormuz on Thursday involving more than 50 small boats, practicing “swarming” operations that could potentially shut down the vital water way if ever deployed for real, U.S. officials said.

The drill, which officials anticipate will end in a matter of hours since the gun boats are small, comes after President Trump pulled the U.S. out of a landmark nuclear accord with Iran and leaders of both countries exchanged fiery rhetoric.

"We are aware of the increase in Iranian naval operations within the Arabian Gulf, Strait of Hormuz and Gulf of Oman," Navy Capt. Bill Urban, a U.S. Central Command spokesperson, said in a statement. "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.”

Roughly 10 percent of the world’s oil passes through the Strait of Hormuz.

U.S. officials say there has been no indication of any threats to American forces.

Currently, the guided-missile destroyer USS The Sullivans is in the Persian Gulf. Some British and French warships are nearby in the region. There are also 10 American patrol craft based in Bahrain at the headquarters for the U.S. Navy’s 5th fleet.

The U.S. destroyer is part of the Harry S. Truman aircraft carrier strike group, but the aircraft carrier is not in the Persian Gulf or surrounding area right now, having returned to Norfolk, Va. late last month following a three-month deployment.

The Trump administration plans to impose more sanctions on Iran next week, drawing the ire of senior Iranian leaders.

Trump said Monday, however, he would be willing to meet with Iranian President Hassan Rouhani with “no preconditions.”

Iranian officials the next day rejected Trump's overture.

Since the U.S. pulled out of the nuclear deal, Iran’s currency has plummeted, drawing thousands of protesters across major cities in Iran in recent weeks.