The U.S. Navy announced on Thursday it is doubling the number of minesweeping ships and helicopters based in the Gulf, AFP reported.

The announcement comes amid growing tensions over Iran’s threats to close the strategic Strait of Hormuz.

The top U.S. Navy officer, Admiral Jonathan Greenert, told lawmakers the United States plans to send four minesweeping ships along with mine-hunting helicopters to the region, bringing the total to eight for each type of asset.

“I wanted to be sure… that we are ready — that our folks are proficient, they’re confident and they’re good at what they do in case called upon,” Greenert was quoted by AFP as having told the Senate Armed Services Committee.

The move to boost U.S. defenses in the region comes amid heightened tensions with Iran, after it threatened to close the Strait of Hormuz, a key transit route for global oil supplies, in response to Western sanctions over Tehran’s nuclear program.

Four minesweeping ships are currently based in Bahrain, headquarters of the U.S. Fifth Fleet, according to the report. The U.S. Navy has a total of 14 of these ships, and it also plans to improve submarine drones that can neutralize mines, the report said.

Iran recently announced it had deployed warplanes and missiles in an ‘exercise’ to protect its nuclear sites from attack.

Meanwhile on Thursday, the sanctions against Iran continued and the Society for Worldwide Interbank Financial Telecommunication, or SWIFT, announced that it is cutting off some 30 Iranian banks and subsidiaries from its network. The banks punished are the ones that have already been hit by European Union sanctions.

Some other Iranian banks remain unaffected by the move, which will go into effect about 48 hours after the announcement.