MOGADISHU, Somalia (AP) _ A U.S. Army employee was killed and three other American civilians wounded by an anti-tank mine today as they scouted the area near Bardera, the next destination of the Marines' mercy mission.

The death was the first of an American since Marines came ashore in Mogadishu on Dec. 9 as the vanguard of a U.S.-led multinational force to safeguard the delivery of food to Somalia's starving.

The four, three of them State Department security personnel, were on a reconnaissance mission in preparation for a planned Christmas Eve push into Bardera, Marine spokesman Col. Fred Peck told reporters in Mogadishu.

He said the Army employee was killed instantly. He would not say what he or the security officers were doing.

Marine Lt. Gen. Robert Johnston, the commander of U.S. forces in Somalia, told ABC's ''Good Morning America,'' ''We knew, especially when we approached places like this, that the concerns regarding mines would be magnified. We have done everything we could to mark them.''

Forces will be even more diligent in looking for mines, but their mission will not change, he said.

A White House statement said: '''We regret the loss of life. The Operation Restore Hope will continue as planned, and we don't expect it will have any effect on the president's trip.''

President Bush is to visit U.S. troops in Somalia for New Year's. The White House announced Tuesday that he would arrive on Dec. 31.

The wounded Americans were taken to the USS Tripoli, an amphibious assault ship off the Somali coast, where one was in critical and two were in stable condition. A second mine was found in the area, Peck said, but he did not know if the mines were newly laid - and perhaps directed at the foreign troops - or among the many explosives put down by factions involved in the country's civil war.

Roads and trails around Bardera have been mined in recent weeks by the warlord holding the town, Mohamed Said Hirsi, a son-in-law of former dictator Mohammed Siad Barre known as Gen. Morgan.

Peck said residents are familiar with most of the mine fields and have marked safe paths around them.

The Americans ''were traveling in an area where it was assumed all known mines were marked,'' Peck said, and were alone in a ''civilian vehicle'' about a half mile north of Bardera's airfield.

At a later briefing, he indicated the four were not traveling along the same route troops intend to take when they move into Bardera on Thursday. Mine-sweeping was planned as part of the troop move, he said.

Peck said the Americans' names would be released after their families were notified.

The Army employee was the third foreigner killed since the Marines arrived. The other two were aid workers from Bulgaria and Belgium.

U.S. special envoy Robert Oakley flew to Bardera later today to talk with clan elders and community leaders in advance of the Marines' arrival. Peck said he had no detail about Oakley's talks.

On Tuesday, Peck said no opposition was expected in either Bardera or Hoddur, where Marines are headed on Christmas. Hoddur is about 90 miles north of Baidoa.

Both towns are important distribution points for aid in a country where famine has taken up to 350,000 lives and threatens 2 million more.

The Marines planned to leave Baidoa at first light Thursday and seize Bardera's airport before sundown. Two companies of French paratroopers and one company of Marines were to then take Hoddur.

Oakley had not planned to meet today with Gen. Morgan. The U.S. special envoy also visited Mogadishu, Beli Dogle and Baidoa and met with local warlords before coalition forces moved into those towns.

Gen. Morgan was among the most ruthless commanders in Siad Barre's army. He planned and executed the bombing raids that reduced the northern Somalia town of Hargeisa to rubble in the civil war that preceded the dictator's January 1991 downfall.

Even as Operation Restore Hope progresses, the argument over the mission's goals intensified.

U.N. Secretary-General Boutros Boutros-Ghali, who insists the U.S.-led force disarm roving gunmen and set up a police force before heading home, met in New York on Tuesday night with Secretary of State Lawrence Eagleburger.

No one commented on the meeting's outcome.

Eagleburger then sat in with a group of U.N. and U.S. officials to try to resolve differences that Boutros-Ghali has not hesitated to publicize, most recently in a weekend letter to the Security Council released on Monday.

Bush wants to quickly wrap up three-week-old Operation Restore Hope and have U.N. peacekeepers replace the Americans, who argue that disarming is not feasible militarily, or desirable politically.

Critics of the U.S. plan argue that the looters who plagued relief efforts before the Marines landed - and are now lying low in areas foreign forces have reached - would quickly resume their pillaging.

Washington's hopes that a conventional U.N. peacekeeping force will swiftly replace the U.S. troops. Bush would like to pull out Americans next month.

Peck said Tuesday that the operation was about two weeks ahead of schedule, largely because it has met no opposition.