U.S. Seeks to Head Off China A-Test : Weapons: A nuclear explosion would weaken international efforts to ban all testing.

Concerned by intelligence reports suggesting that China may soon conduct a major nuclear test, the Clinton Administration for the past several weeks has conducted an intensive, high-level diplomatic campaign to prevent Beijing from resuming nuclear testing, senior U.S. officials disclosed Thursday.

Administration officials acknowledged, however, that their effort may not be successful and that China may be about to carry out an underground nuclear explosion at its nuclear test facility at Lop Nor in the Xinjiang region of northwestern China.

“We would view a Chinese nuclear test with serious concern,” a senior Administration official said in a statement Thursday night.

The dispute over nuclear testing is the clearest and most serious indication to date of the friction between the United States and China. Over the last three months, Washington and Beijing have also sparred with one another over other arms proliferation issues, human rights and China’s bid, to be decided Thursday, to host the Olympic Games in the year 2000.

Any Chinese nuclear explosion would also deal a major, if not fatal, blow to an international campaign to arrange a nuclear test ban. After considerable hesitation, the Clinton Administration recently agreed to suspend U.S. nuclear testing but left the door open to resume tests if other nations did not stop as well.

Some Pentagon officials have made it clear they would like to start nuclear testing again, and they are sure to point to any Chinese test as justification for a change in American policy.

A senior Clinton Administration official said Thursday night that “we have been engaged actively for several weeks to dissuade China from carrying out such a test. “Very senior” Clinton Administration officials have been involved in this effort, as well as “a large number” of other governments, he said.

China became a nuclear-weapons state in 1964. After trying and failing to obtain nuclear weapons from the Soviet Union, Chairman Mao Tse-tung and other Chinese leaders developed the bomb with the help of a leading Chinese-American nuclear scientist who had returned home to China.

Over the last three decades, China is believed to have carried out 38 nuclear tests. The United States has tested nuclear weapons more than 900 times, and the Soviet Union carried out more than 700 tests.

By far the biggest nuclear explosion in the world in recent years was the huge underground test China carried out at Lop Nor in the spring of 1992. The test measured about 1 megaton, or 1,000 kilotons, equivalent to 1 million tons of TNT.

That Chinese device was many times larger than the United States or Russia would be permitted to detonate under existing arms control treaties, the George Bush Administration said at the time.

Last July, President Clinton announced he would extend for at least 15 months the U.S. moratorium on underground nuclear testing.

“If, however, this moratorium is broken by another nation,” he warned, “I will direct the Department of Energy to prepare to conduct additional tests, while seeking approval to do so from Congress.”

The controversy is the third in the past year in which Defense Department, intelligence and arms-control officials have sought tough U.S. action against China.

The first involved reports that China was exporting elements of its new M-11 missiles to Pakistan.

The second controversy arose after U.S. intelligence officials reported in July that a Chinese ship was exporting to Iran two dangerous chemicals that can be used to manufacture poison gases. But an inspection of the ship uncovered none of those chemicals.