Pentagon officials have decided to order an additional force of mine-sweeping ships to the Persian Gulf and to create a special command to take direct charge of the escalating U.S. military presence there, sources said yesterday.

At the same time, Pentagon officials are preparing to recommend that some U.S. military personnel serving in the region receive "imminent danger pay" under certain conditions, according to sources.

Meanwhile, the third convoy of former Kuwaiti tankers now flying the U.S. flag moved into the Persian Gulf yesterday escorted by three U.S. Navy warships and the assault ship USS Guadalcanal with its sophisticated mine-sweeping Sea Stallion helicopters combing the waters ahead of the ships for submerged mines. {Details on Page A25.}

The new developments outlined yesterday signal that Pentagon officials expect to be involved in Persian Gulf operations for a long time.

Even before these moves, some members of Congress argued that the War Powers Resolution should be invoked, to permit Congress to decide whether U.S. warships should continue to escort reflagged Kuwaiti tankers. More than 100 members of Congress, most of them Democrats, have asked a federal court to order President Reagan to invoke the resolution.

"There's no change in our position that notification of Congress under the War Powers Resolution is unnecessary," White House spokesman Marlin Fitzwater said in Santa Barbara, Calif., where the president is vacationing.

White House officials made similar statements last week after a Navy fighter fired two missiles, apparently at an Iranian plane that was approaching a U.S. plane in the gulf. The plane was not hit.

The White House view is that hostilities are not "imminent" in the gulf. If the White House found that hostilities were imminent, Reagan would be required to notify Congress under the War Powers Resolution.

The United States is amassing in the area one of its largest military buildups since the Vietnam war, having ordered almost 40 ships and small surface craft to the region in addition to numerous aircraft and several groups of elite special forces units.

The Navy is preparing to send several ocean mine sweepers to the gulf in ddition to the four small coastal mine-sweeping ships and eight Sea Stallion helicopters that already have been assigned to help protect the former Kuwaiti oil tankers and their U.S. escorts, Pentagon sources said.

Fitzwater confirmed the move, saying the addition to the mine-sweeping capability of the U.S. forces was consistent with the president's commitment to maintain free navigation in the Persian Gulf.

The aging, wooden-hulled ocean mine sweepers are expected to take more than a month to reach the Persian Gulf from their home ports on the West and East coasts, sources said. Sources said the 172-foot ships, most of them more than 30 years old, probably would be towed across the ocean to reduce wear and tear on engines and other parts.

The Tacoma (Wash.) News Tribune reported that up to five of the ships have received orders to leave Bremerton, Wash., while The Norfolk (Va.) Ledger-Star reported that three ships are scheduled to leave from Norfolk. Pentagon sources said at least one mine sweeper has been ordered to the gulf from Charleston, S.C.

If all are sent, they would represent almost half of the nation's ocean-going mine-sweeping force of 21 ships. Only three of those ships are fully manned by active-duty crews. It is unclear whether the Navy plans to use some reserve sailors and officers to operate the ships in the gulf.

In an effort to improve coordination of the growing U.S. military forces in the Persian Gulf region, top military leaders have agreed to establish a special command -- based in or near the region -- to oversee operations, sources also said.

The decision to create the new command, which would have authority over the two-star admiral who now heads the Middle East Task Force, followed weeks of bitter internal bickering between the Navy and the joint services Central Command, based in Tampa, Fla. Although mainly Navy equipment and personnel are being used in the gulf region, the Central Command, headed by a four-star Marine general, controls the operation.

That has frustrated naval officials and reopened old political wounds among some service officials who resented the creation several years ago of the joint command and the power it wields over the individual services.

The new Persian Gulf commander would coordinate activities in the gulf and report directly to the Central Command, which in turn reports to the Joint Chiefs of Staff, according to sources familiar with the proposal. Sources said the commander would be a naval officer. The Navy earlier had proposed that a three-star admiral hold the position.

"As long as we have a multifaceted activity out there, it's the way to go," said one source.

At the same time, Pentagon officials are preparing a proposal that would allow some military personnel in the Persian Gulf region to receive an extra $110 a month in "imminent danger pay," sources said. Congress is considering a measure that would require the Defense Department to pay the bonuses to all military personnel serving in the gulf.

One source said the bonus would be paid only "under certain circumstances," but did not say what those circumstances would be.

Defense Department policy allows field commanders to recommend danger pay for their sailors and troops, based on individual situations.

The department's policy also allows the commanders of certain regions or service secretaries to recommend the pay for military personnel serving in dangerous geographical areas.

The recommendation then must be approved by the Joint Chiefs of Staff and Defense Secretary Caspar W. Weinberger, according to a Defense Department spokesman. Staff writer Lou Cannon contributed to this report.