Adding to the mix, a new human resources report by an independent consultant has sharply criticized the Vienna-based monitoring organization's management and personnel practices.

One diplomatic source said he feared the test ban regime was starting to "unravel" from within as well as from without.

The United States, the leading nuclear power, dealt a stinging blow to the 1996 Comprehensive Test Ban Treaty, or CTBT, when the Senate refused to ratify it in 2000.

Since then, President George W. Bush has reiterated his firm opposition to the treaty, although his administration has pledged to continue paying most, but not all, of the $18 million annual U.S. share of the CTBT organization costs.

The U.N. administrative office has operated in Vienna for five years, gathering data and establishing an elaborate system of 337 sensors around the world designed to measure and verify the test ban if the treaty ever enters into force.

China, Iran and several other countries have expressed dismay at being asked to commit millions of dollars to the monitoring operation when it was unclear when - or if - the treaty might actually take effect.

The operation is costing a total of $85 million-$90 million annually with no substantial decline in sight, officials said.

The CTBT, banning all nuclear blasts in the atmosphere, in space and underground, has been signed by 165 states. Of those 89 have ratified it.

44 STATES KEY TO APPROVAL

But it has not taken effect because it must be ratified by 44 states specifically deemed nuclear arms-capable, including the United States, China, Iran, India and Pakistan. Only 31 of those have ratified it.

China has four monitoring stations on its territory but has yet to install the communications facilities to transmit data to the international collection center in Vienna, U.S. officials said.

There are other seismic stations in China in a cooperative agreement with the U.S. Geological Survey, but Beijing has stopped transmitting data from these stations in real time directly to Vienna, instead sending the information via computer diskettes in a diplomatic pouch, they said.

A U.S. official said "there may be political aspects to the Chinese dragging their feet," namely a recent U.S. decision to only pay costs associated with the monitoring system, not other functions of the Vienna-based CTBT organization.

A monitoring station in Iran became operational last year but Tehran recently stopped sending data to Vienna after a few months, a U.S. official and diplomatic source said.

This suggests Iran may be joining China in an effort to get back at Washington for withholding partial funding from the CTBT organization and also for Bush's recent description of Iran as an "axis of evil" with Iraq and North Korea, the sources said.

"China, Iran and others feel the United States shouldn't be getting a free ride" by picking and choosing its degree of cooperation with the CTBT regime, a U.S. official said.

If other countries also began to withhold cooperation and funding, "then the whole thing could unravel," he said.

Meanwhile, advocates of the test ban operation worry a consultant's report critical of the CTBT organization's management and personnel practices could provide further ammunition for critics, especially if changes are not made.

The report, obtained by Reuters, found a "consistent message of fear and mistrust" in the organization's 260-member secretariat and reported that some employees feel political concerns are more important than technical requirements.

It also warned the organization faces a severe brain drain.

A spokeswoman for the CTBT organization, Daniela Rozgonova, said the human resources report and the monitoring operations were "two distinct matters" and the management was addressing recommendations for change contained in the report.