The United States was informed Sunday that one of two pilots involved in the downing of a U.S. helicopter in North Korea was killed, prompting President Clinton to decry "this tragic loss of life" as unnecessary and press for the return of the survivor.

In a statement issued from the White House, Clinton announced the startling development, which came to the attention of the United States a full 36 hours after the unarmed U.S. Army OH-5KC observation helicopter strayed into North Korean airspace and was forced to land under disputed circumstances.U.S. officials have claimed the helicopter was on a routine orientation mission, while Pyongyang said its anti-aircraft gunners shot down an "enemy" helicopter that crossed the heavily armed border and flew into Kangwon Province in southeastern North Korea.

Clinton said Pyongyang had informed the United States of the death of Chief Warrant Officer David Hilemon of Clarksville, Tenn., through Rep. Bill Richardson, D-N.M., who was in the country visiting.

The other crewman, Chief Warrant Officer Bobby Hall of Brooksville, Fla., "is alive and reportedly uninjured," the president said. Both were members of the 501st Aviation Regiment of Camp Page, in South Korea.

The troubling incident comes as U.S.-North Korean relations had appeared to be warming after decades of mistrust compounded by concern over Pyongyang's nuclear program.

Clinton said he had directed Richardson to remain in the communist capital and that the congressman "has at my instructions told the North Korean government that we want prompt access to Chief Warrant Officer Hall and his return to a U.S. facility along with the remains of Chief Warrant Officer Hilemon."

Hall has been in custody since his chopper went down as far as five miles within North Korean territory in the evening of Dec. 16, U.S. time (0230 GMT Saturday).

"We are using all available channels to press for an early resolution of this matter," Clinton said.

Secretary of State Warren Christopher also has told North Korean government representatives in New York that the United States wants the Americans back while the investigation continues into whether they were shot down or were the victims of mechanical difficulty.

Word of Hilemon's death caught many U.S. officials by surprise although it has been historically difficult to glean information in the closed society of Pyongyang. The situation has only intensified by the uncertainty following the July death of Kim Il Sung, who had ruled North Korea with an iron fist since the communist nation was formed in the wake of World War II.

The circumstances surrounding the incident remained unclear. Until Sunday, U.S. officials had been unable to even determine the fate of the pilots, who were apparently forced to land in the restricted buffer zone on the North Korean side of the demilitarized zone separating the two countries.

South Korea's Yonhap News Agency had reported that neither was injured when the chopper went down.

Defense Secretary William Perry insisted the helicopter was on a routine training mission and was not involved in any espionage.

An administration official was loathe to characterize the development as a possible setback in relations between Washington and Pyongyang, which after about 18 months of standoff recently reached agreement under which North Korea pledged to give up activities suspected of being aimed at developing a nuclear bomb. In exchange, it will receive two modern nuclear reactors at an estimated cost of $4 billion, paid for mainly by South Korea and Japan.

Clinton, who officials said was hopeful the situation could be resolved quickly and completely, said, "This tragic loss of life was unnecessary."

"Our primary concern now is the welfare of Chief Warrant Officer Hall and his return along with the body of Chief Warrant Officer Hilemon. Congressman Richardson, who has worked tirelessly to resolve this matter over the past two days, is staying in North Korea for now and will remain in constant contact with North Korean officials on our behalf," Clinton said. "Our thoughts and prayers are with the families of both of these aviators."

Richardson, a member of the House intelligence committee, was in the country on the first leg of an Asian fact-finding tour.