WASHINGTON (AP) _ NASA officials pressured a former budget analyst to lie about the space agency's follow-up to safety issues he raised regarding the space shuttle's O- ring seals six months before the Challenger explosion, the analyst said in a published account.

Writing in an opinion-page article in Sunday's Washington Post, Richard C. Cook said, ''I felt I was under official orders to deny publicly the validity of my earlier July 23 memorandum, a denial which of course I could not and did not make.''

Cook said that six months before the Jan. 28 explosion that killed the Challenger's crew of seven he wrote a memo ''summarizing my concerns about the safety of the solid rocket booster used in the space shuttle.''

As the post-accident probe was getting under way and news media inquiries mounted, ''I was told to say that after I filed my report, the problem was discussed in the comptroller's office, inquiries were made to the program office, and work was under way that satisfied us that the safety issue was being dealt with,'' he wrote in the newspaper.

Cook, who now works for the Treasury Department, also said the promotion system at the National Aeronautics and Space Administration tends to ''turn people into yes men'' with a ''decided tendency to report only good news, to paint only a rosy picture.''

Jim McCulla, deputy director of public affairs at NASA headquarters in Washington, said he found Cook's comments about being told what to say to reporters incredible.

''I've never heard any of that. I can't imagine that,'' McCulla said. ''NASA has always had since its inception a rule that says that any member of the press can go to anybody (in NASA) and talk to them.''

Since Cook didn't name the NASA superior who allegedly told him what to say, McCulla said there was no way to know what he meant.

Cook wrote his memo after investigating the possible budgetary impact of the O-ring seal problem. The investigation of the Challenger explosion has highlighted possible failure of the O-rings, which are designed to contain hot exhaust gases in the shuttle's rocket boosters.

In his article, Cook wrote that NASA ''people understood completely the implications of a possible O-ring failure. It's just that it was viewed as no problem.''

At NASA, in the hours and days following the accident, ''there were who might be blamed,'' Cook wrote.

Cook concluded that if NASA had listened to ''a small number of individuals ... who feared that the booster seals were unreliable in cold weather ... the Challenger and its astronauts might still be with us today.''