NEW YORK, SEPT. 29 -- Secretary of State James A. Baker III and Vietnamese Foreign Minister Nguyen Co Thach today held the first high-level meeting between officials of their two countries since 1973, two years before the end of the Vietnam War.

U.S. officials called the meeting a "step in the direction" of further normalization of relations and announced that Thach will be permitted to go to Washington in the next week or so to meet with Gen. John Vessey Jr. The former chairman of the Joint Chiefs of Staff is the special U.S. negotiatior for resolving the issue of 1,678 American servicemen lost in Vietnam whose status still is not formally resolved.

Thach is likely also to meet with the Senate Foreign Relations Committee, which had invited him for an informal, closed-door discussion. Thach had told the committee he would attend if the State Department lifted its restriction prohibiting officials of Vietnam's Communist government from traveling beyond a 25-mile radius of their mission at the United Nations.

Before his meeting with Baker, Thach acknowledged that Vietnam, which apparently has withdrawn its troops from Cambodia, still has military advisers there. He said Hanoi is willing to pull the advisers out of Cambodia, but he gave no timetable for their withdrawal and did not specify how many advisers are there. "We have promised to have international monitoring of our withdrawal," Thach told reporters. "We have withdrawn our forces, and we will withdraw all our advisers."

Vietnam invaded Cambodia in 1978 to oust that nation's Communist Khmer Rouge government. The next year, Vietnam installed a friendly government in Phnom Penh that became embroiled in a civil war with a three-faction guerrilla coalition that includes the Khmer Rouge.

Vietnam withdrew its troops from Cambodia last year, and the guerrillas and the Cambodian government this month agreed to abide by a U.N. plan to end the conflict.

Baker and Thach met for about 30 minutes with aides present and then met briefly in private, a senior State Department official told reporters. Baker pressed Thach for a full accounting by Vietnam of the American personnel, the official said.

State Department spokesman Margaret Tutwiler said in a statement that Baker urged Thach to move on the issue of the servicemen so that both countries would be in a position to move quickly toward normal relations once a settlement is reached to end the civil war in Cambodia.

Baker noted that "significant progress had been made . . . in recent months on" achieving a settlement in Cambodia, the official said, and "noted our belief that Vietnam has played a constructive role in these developments."

The missing servicemen and the Cambodian question are the two main obstacles to normalizing relations between the United States and Vietnam.

The United States has no diplomatic relations with Hanoi, classifies it as an enemy and recently extended a ban on trading with it. The ban and U.S. opposition to lending to Vietnam by international banks have affected the country's economy and it no longer can count on aid from the Soviet Union and East European countries.

The situation has caused substantial tension within Vietnam's ruling Politburo. Thach is generally considered to be a leader of a moderate faction within the 14-member body, advocating a more open economy, Western investment and better relations with the United States as the only way to solve Vietnam's economic woes.

U.S. policy toward Vietnam has warmed substantially since July 18, when Baker announced that the administration would discuss Cambodia with Vietnamese officials in New York.

Baker also met today with Japanese Foreign Minister Taro Nakayama, and Japanese officials said Baker had asked Japan for additional financial aid to help pay for the military buildup in the Persian Gulf region.

Japan has promised $4 billion to assist the U.S. forces and cushion the effects on some countries of a U.N. commercial embargo against Iraq.

The U.S. official said it would be misleading to say the emphasis of the meeting had been on financial contributions and that they had discussed the entire gulf situation.