WASHINGTON — The Navy is rushing tiny underwater drones to the Persian Gulf to help find and destroy sea mines as part of an American military buildup aimed at stopping Iran from closing the strategic Strait of Hormuz in the event of a crisis, U.S. officials said.

Only 88 pounds and 4 feet long, the unmanned, remotely guided submersibles carry a TV camera, homing sonar and an explosive charge for what amounts to a kamikaze mission: When it detects a mine, the undersea craft obliterates itself as well as the mine.

The Navy bought dozens of the little-known German-made devices, known as the SeaFox, in February after an urgent request by Marine Gen. James Mattis, the top U.S. commander in the Middle East, for more minesweeping capabilities in the region, officials said.

The first drones began arriving in recent weeks as the latest round of negotiations with Iran over its disputed nuclear development program appears to have stalled. Renewed diplomatic talks between Iran and the five permanent members of the United Nations Security Council plus Germany have failed to achieve a breakthrough or lessen tensions.

Some U.S. officials worry that Iran may respond to the West’s tightening sanctions on its banking and energy sectors, including a European Union oil embargo, by launching or sponsoring attacks on vulnerable oil tankers or platforms in or near the crucial strait.

Some officials in Tehran have threatened to close the narrow waterway between Iran and Oman, a choke point for a fifth of the oil traded worldwide, using sea mines, speedboats and coastal missile batteries against military or commercial targets. Pentagon planners take the threat seriously, although analysts doubt Iran would risk provoking a direct conflict with the United States.

Reopening the strait could take the Navy and its allies five to 10 days, officials said. But experts say even a temporary disruption of tanker traffic could cause global oil prices to soar and spark widespread economic turmoil.

Along with the new submersibles, the Pentagon recently added four minesweeping ships, bringing the total in the area to eight, and four MH-53 minesweeping helicopters. They reinforce a growing U.S. naval, air and ground force aimed at countering Iran, and reassuring Israel, in an uncertain environment.

The Obama administration previously sent two aircraft carriers and a squadron of F-22 fighter jets to the region and is keeping two Army brigades in Kuwait. The Pentagon has acknowledged those deployments, but has not publicly disclosed sending underwater drones, apparently to avoid alerting Iran.

The technology for the drones, which cost $100,000 each, is hardly new. Andy Culbreath, vice president of business operations at Atlas North America, a subsidiary of the German company that manufactures the SeaFox, said the torpedo-like submersibles have been available for a decade and are used by about 10 other countries, including Britain.

The device is controlled by a 3,000-foot fiber-optic cable and sends live video back to a camera operator at a console. It operates up to 984 feet deep and travels at a speed of up to 6 knots.

Christopher Harmer, a retired Navy commander who served as director of future operations at U.S. 5th Fleet headquarters in Bahrain, said the system can be deployed from minesweepers or other ships, as well as from helicopters and small boats, augmenting the Navy’s anti-mine capabilities.

“In the Cold War, minesweeping warfare was a large part of what the Navy did, but we have lost a lot of our minesweeping capability,” said Harmer, a senior analyst at the Institute for the Study of War, a Washington think tank. “The SeaFox is a relatively simple, off-the-shelf system that we can put off our minesweepers but also any surface ship.”

Iran’s ability to block the strait has grown in recent years because it has built mini-submarines that are difficult to track and that can be used to place underwater mines, Harmer said. Iran also can drop mines from ships or from bases onshore, using gulf currents to position them near the strait, he said.

During its 1980-88 war with Iraq, Iran mined shipping routes and threatened to close the strait. When the Samuel Roberts, a guided-missile frigate, was severely damaged by an Iranian mine in 1988, the Reagan administration ordered the destruction of two Iranian oil platforms, an Iranian frigate and a number of missile boats.

Iran probably would face a similar or even more devastating response if it tried to mine the strait today, Harmer said. “If they wanted to close the Strait of Hormuz, they could do it, but they would only be able to do it one time,” he said.

In a recent unclassified report to Congress, the Defense Department said Iran’s “conventional military capabilities continue to improve,” citing its “new ships and submarines.”

It noted that Tehran has threatened to close the strait “in response to increasing sanctions and in the event Iran is attacked.”

But the report focused largely on advances in the accuracy and range of Iran’s ballistic missiles and on its support to terrorist groups in the region. It warned that Tehran “has methodically cultivated a network of sponsored terrorist surrogates capable of targeting U.S. and Israeli interests.”

david.cloud@latimes.com