Mine-sweeping teams have discovered a mine field in the Persian Gulf near where a reflagged Kuwaiti supertanker escorted by U.S. Navy warships hit a mine last Thursday, increasing concern over the lack of long-term plans for protecting convoys through the treacherous channels, Pentagon officials said yesterday.

U.S. explosives-disposal teams have been dispatched to help clear the mines from waters off Farsi Island about 120 miles southeast of Kuwait, officials said. Pentagon officials said Saudi, Kuwaiti and U.S. mine-sweeping teams think that they have identified seven mines in the area but are uncertain how many more may have been laid in the channel.

Pentagon officials said the discovery of the mine field raises new concerns about U.S. warships and the reflagged tankers in the gulf, prompting military and diplomatic leaders to intensify efforts to protect future escorted convoys through the region.

"They're scared," said one Pentagon official, describing the reaction of the Navy crews involved in the controversial escort operations. "This means we have to do something, the contingency plans have to be accelerated."

Meanwhile, shipping officials in Kuwait yesterday said they have received informal U.S. Coast Guard approval to partially load the damaged Bridgeton with oil and send it back down the Persian Gulf with a U.S. escort on Friday. But in Washington, a Coast Guard spokesman said official approval had not yet been issued.

Defense and State Department officials drew a distinction between immediate, makeshift methods of protecting the first two reflagged Kuwaiti ships on their way out of the Persian Gulf and longer-term arrangements, still under discussion, for protecting future convoys of oil tankers and U.S. warships through the gulf.

A senior State Department official said various mine-protection plans for "the medium term" are being considered by the administration, ranging from improved U.S. access to facilities in Kuwait and Saudi Arabia to assistance in mine-sweeping from British or Dutch military forces. He hinted that another possibility under discussion is purchase either by the United States or a gulf nation of modern mine-sweeping ships from the Dutch.

The U.S. Navy has no mine-sweeping ships in the Persian Gulf region. Of the Navy's 21 aging mine-sweepers, only three are manned by active duty crews. Helicopters are used for most mine detection and no gulf state has allowed the United States to base the aircraft on their soil. There had been no U.S. mine-detection operations where the Bridgeton was damaged.

"This type of warfare is really never-ending," said one Pentagon official. "You can never be satisfied with what you've got. You could find seven mines or a dozen mines and then, in the black of night, an adversary like Iran could come out and drop another dozen."

Iran has not claimed it was behind the Bridgeton incident, saying it was the work of "invisible hands."

Assistant Secretary of State Richard W. Murphy came under heavy fire at a House subcommittee hearing yesterday for the administration's refusal to accept earlier congressional demands that the reflagging and protection of Kuwaiti ships be put off for a limited time pending fuller consideration and more adequate protective arrangements.

Murphy said the mine damage to a reflagged ship on the second day of its first voyage under U.S. naval protection was "an embarrassment, no question." But he maintained that "a delay would have had significant costs on the political side based on our assessment of the mood in the {Persian Gulf} region."

He told the House Foreign Affairs subcommittee on Europe and the Middle East that even a 30- or 90-day congressionally mandated delay of reflagging would have given "a signal" to Tehran authorities that they had won a battle in the United States "through their manipulation of opinion and manipulation of the media."

Pentagon officials said it is uncertain whether discovery of the mine field will alter schedules to escort the Bridgeton and reflagged Gas Prince out of the gulf or change plans for the second escort, scheduled for next week. Murphy testified that "we expect there will be a second convoy shortly and, once all 11 {Kuwaiti} ships are re-registered, five or six convoys each month."

Pentagon spokesman Robert B. Sims said at a news briefing yesterday that military officials believe the mine that blew a massive hole in the hull of the supertanker Bridgeton last week was planted only hours before two reflagged tankers and three U.S. Navy escort ships steamed through the channel.

Other Pentagon officials say they believe the additional mines discovered last weekend were moored in the waters at the same time. Those officials also say they believe the mines were planted by Iranians.

"It looks like the same modus operandi," said one Pentagon official. "The invisible hand strikes again."

The mines discovered in the shipping channel are of the same type of pre-World War I design as those found near the entrance of the Kuwaiti harbor earlier this summer, according to sources familiar with the operations. The United States sent 18 explosive ordnance-disposal experts to help Saudi and Kuwaiti mine-sweeping teams in that operation. The same experts are helping clear the newly discovered mine field.

The explosives teams operate off small boats, dropping charges through the water onto the mines. The ensuing detonation is just forceful enough to deactivate the mine without causing it to fully explode. The mine then usually is towed to a safe shore location for detonation or analysis.

Military leaders are considering basing mine-sweeping Sea Stallion helicopters on U.S. ships in the region, including the command ship USS LaSalle now in the gulf.

State Department officials said they are continuing diplomatic discussions with other nations to help provide mine-sweeping capabili- ties.

Military officials said the U.S. Navy can conduct some limited mine-sweeping operations with small antisubmarine-warfare helicopters now stationed aboard frigates in the gulf.

But one Pentagon official said Navy leaders are eager to send the Sea Stallion helicopters, with more sophisticated mine-sweeping capabilities.

The official said some Navy officials consider it politically too embarrassing to use large tankers such as the Bridgeton to protect smaller U.S. warships from mines.

The mine explosion only slightly damaged the Bridgeton, but Pentagon officials said it would have sent the USS Crommelin, one of the escort ships, "to the bottom."