Updated

The Pentagon is beefing up U.S. sea- and land-based defenses in the Persian Gulf to counter any attempt by Iran to close the Strait of Hormuz.

The U.S. military has notified Congress of plans to preposition new mine-detection and clearing equipment and expand surveillance capabilities in and around the strait, according to defense officials briefed on the requests, including one submitted earlier this month.

The military also wants to quickly modify weapons systems on ships so they could be used against Iranian fast-attack boats, as well as shore-launched cruise missiles, the defense officials said.

The readiness push is spearheaded by the military's Central Command, which oversees U.S. forces in the Gulf region, these officials said. It shows the extent to which war planners are taking tangible steps to prepare for a possible conflict with Iran, even as top White House and defense leaders try to tamp down talk of war and emphasize other options.

The changes put a spotlight on what officials have singled out as potential U.S. shortcomings in the event of conflict with Iran. The head of Central Command, Marine Gen. James Mattis, asked for the equipment upgrades after reviews by war planners last spring and fall exposed "gaps" in U.S. defense capabilities and military preparedness should Tehran close the Strait of Hormuz, officials said.

The Central Command reviews, in particular, have fueled concerns about the U.S. military's ability to respond swiftly should Iran mine the strait, through which nearly 20% of the world's traded oil passes.

"When the enemy shows more signs of capability, we ask what we can do to checkmate it," a U.S. military officer said. "They ought to know we take steps to make sure we are ready."

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