Two days from the start of a UN conference promoting a global ban on nuclear weapons tests, the United States has not decided whether to attend the meeting and may boycott it, US and UN officials say.
Arms control experts close to the decision making process said no decision has been made but Washington was leaning heavily against attending the three-day conference on the Comprehensive Test Ban Treaty (CTBT), which begins on Sunday.
The Pentagon, hoping to hasten the treaty's death, has been pressing the administration for months to sit out the meeting, which initially was scheduled for late September but postponed after the September 11th suicide airliner attacks on New York.
The CTBT, which has not yet entered into force because it has not garnered the necessary ratifications, would ban all nuclear blasts, whether in the atmosphere, in space or underground. A 1963 treaty barred tests in the atmosphere and another one in 1974 set limits on underground explosions.
The George W. Bush administration worries that without testing, it cannot ensure the safety and reliability of US nuclear arms. Critics say simulated testing conducted via computers and other technology is sufficient.
US officials insist President Bush remains deeply concerned about nuclear proliferation and expects to continue abiding by a testing moratorium put in place by his father in 1992.
But critics say a boycott of the UN conference would be a powerful message to allies strongly backing the CTBT that Washington wanted to go it alone on nuclear arms control.
"This will not be the last word. But it's a sad commentary on the Bush administration's approach to post-September 11th weapons-of-mass-destruction challenges," said Mr Daryl Kimball, executive director of the Washington-based Arms Control Association.
"Just as we cannot fight global terror alone, we cannot alone fight the proliferation of nuclear, chemical and biological weapons," he said.