U.S. and Russian defense officials have agreed to set up a joint center in Colorado to watch for any false alarms of missile attacks caused by Year 2000 computer problems, the Defense Department said yesterday.

Defense Secretary William S. Cohen and his Russian counterpart, Defense Minister Igor Sergeyev, will sign an agreement establishing the center during Cohen's visit to Moscow next week, a senior defense official told reporters.

For the last year, U.S. officials have said the Year 2000 computer glitch, known as Y2K, will not cause nuclear missiles to launch. They have portrayed the joint center as a prudent step to avoid confusion in the event early-warning systems or launch detection equipment malfunctioned.

Yesterday, the official, who spoke on condition that he not be identified, said the Pentagon wanted to be clear that neither side was "teetering on the edge of a potential false launch or anything of the sort. We just think it is a very useful thing to extend our cooperation in areas of this nature. . . .

"And at this time of Y2K transition, were there to be some sort of problem, it would certainly be useful to have our people in direct contact and direct communications with one another," the official said.

The official said up to 20 Russian military officers would be assigned to the Center for Strategic Stability and Y2K, at the U.S. Space Command headquarters in Colorado Springs, during late December and early January.

Discussions to set up the center began last year but broke off after NATO bombed Serbia, a Russian ally. The Pentagon official said the talks resumed last month.

Cohen and Sergeyev also will discuss creating a permanent missile early warning system center in Moscow--an idea supported by Presidents Clinton and Boris Yeltsin.

The Year 2000 problem stems from the use in many computer systems of two-digit date fields, which may cause some software and microchip systems to interpret "00" as 1900, not 2000. The confusion could cause the computers to malfunction or stop.

Shortly before the Pentagon announcement, members of Congress who have studied the Y2K problem held a news conference urging the federal government, states and localities to step up the pace of computer fixes and tests.

They also suggested that international air travel could face disruptions because of Y2K problems. "I have no fear of flying on January 1 within the United States. But I think the safety of air travel abroad has yet to be determined," Rep. Jim Turner (D-Tex.) said. Rep. Constance A. Morella (R-Md.) said she has "grave concerns about what's happening outside of the United States."

At the urging of Rep. Stephen Horn (R-Calif.), the Transportation Department released a list of 35 nations who had not responded as of Thursday to a survey by the International Civil Aviation Organization (ICAO). The international aviation group had requested nations to submit Year 2000 computer assessments by July 1.

The nations not responding to the ICAO survey were: Albania, Angola, Bhutan, Bosnia and Herzegovina, Brunei, Burundi, Cambodia, Comoros, Cook Islands, Democratic Republic of Congo, Fiji, Guinea, Iraq, Kiribati, Kyrgyzstan, Lesotho, Libya, Micronesia, Mozambique, Myanmar, Nauru, Nicaragua, Palau, Papua New Guinea, Qatar, Russia, Samoa, San Marino, Sao Tome and Principe, Sierra Leone, Slovenia, Solomon Islands, Tajikistan, Tonga and Vanuatu.

Dave Smallen, the U.S. Transportation Department Y2K spokesman, said: "This is simply a list of countries that did not respond to the ICAO survey. I don't think that you can read anything specific into the fact that any country didn't respond."

Smallen said the Transportation Department and the Defense Department were conducting a review of Y2K readiness and would post information on Transportation's Web site (www.dot.-gov/fly2k) by the end of this month.