The officers of Washington's posh Cosmos Club thought they had finally found a way to defuse the embarrassing controversy over admission policies that has simmered for more than a dozen years. Their solution: to require prospective members to sign an oath stating they will not seek to change the bylaws that exclude women.

Rather than squelching a debate its officers characterize as "unseemly," however, the policy seems likely to revive the furor over letting women join the elite social club that was founded 107 years ago for "men of accomplishment." Among its 3,100 members are Supreme Court Justice Harry A. Blackmun and William E. Colby, former director of the Central Intelligence Agency.

The Cosmos Club is not tax exempt, and thus is under no legal obligation to admit women. Last year the club, located in an ornate Embassy Row mansion valued at $5.1 million at 2121 Massachusetts Ave. NW, paid nearly $104,000 in real estate taxes, city records show.

Within days after the policy was announced earlier this month by the club's board of management in its eagerness to "restore a tranquil and sociable atmosphere," the Committee of Concerned Members of the Cosmos Club, a group favoring the admission of women, hinted it might challenge the policy in court. A lawsuit, Samuel P. Hayes, leader of the Committee of Concerned Members, warned in a recent letter to the board, "could hardly take place without undesirable publicity."

To club members who prize an atmosphere of scholarly gentility so highly that elevator capacity signs are in Latin, the prospect of a court battle is distinctly unpleasant.

"This policy is just total rubbish, especially for a club with intellectual pretensions," said one member of the committee, who requested anonymity because club rules permit only officers to speak to the press. Much of the continued opposition to women, he said, is from many of the club's approximately 300 emeritus members who are over 80 years old.

"Many of them are old men who just like to have a place where they can get away from women," he said.

Other members of the committee, which claims more than 450 supporters, a third of the club's active members, said they suspect the policy was adopted because club officers feared they were gaining enough supporters to vote to change the bylaws or pack the board.

Not so, said club President George E. Hartman, a prominent Washington architect. The policy is not a litmus test but simply an attempt to ensure that prospective members understand the club's rules, according to Hartman. "The board feels that too much energy has been given to a cause which has failed to achieve the necessary support," said Hartman, who claimed that "an active minority is trying to impose its will on a majority."

The new policy, mailed to members with this month's club bulletin, is the latest in a bitter 14-year internal dispute over the admission of women to the elite club.

Last year the 1,500-member University Club changed its bylaws and admitted its first female member, a 32-year-old architect sponsored by her father. Several months later a Maryland judge ruled unconstitutional a state law that granted a property tax exemption to Burning Tree, Bethesda's exclusive all-male golf club.

The Burning Tree ruling has been appealed to the Maryland Court of Appeals, and a decision is expected soon.

At least one other social club in Washington, the Metropolitan Club, remains all-male.

Many athletic and social clubs throughout the country continue to keep their doors closed to women, but a spokesman for the U.S. Golf Association, which is involved with numerous country clubs, said the number is dwindling.

The Supreme Court ruled last year that states could force the Jaycees, a civic and business organization, to allow women to join its clubs. Four months earlier, Washington's Downtown Jaycees had pulled out of the national organization rather than exclude its women members, who constituted about half of the club.

To Cosmos Club members on both sides of the issue, admitting women is not a legal question but a moral one. The club's members have included several presidents, including Woodrow Wilson, jurist Oliver Wendell Holmes, Alexander Graham Bell, scientist Carl Sagan and former secretary of state Henry Kissinger.

Four times since 1971 club members have rejected proposals to admit women. In 1973 in a debate, described in the club's 408-page official history as "polite but pointed," members defeated a proposal to admit women. They did vote, however, that wives and widows of members and female guests were no longer relegated to the "Ladies Entrance" on the side and could use the front door. Women are permitted to eat downstairs but not in the upstairs dining room.

In 1980, 59 percent of the members voted to bar women after opponents, including former club presidents, said they feared admitting women would transform "one of the world's distinguished men's clubs into a mere luncheon group." Earlier this year a slate of "reform" candidates for the board of management was narrowly defeated.

Supporters of the club's single-sex rule say they are loath to alter hallowed tradition and risk incurring the wrath of wives and widows who might then complain that they were "second-class citizens" in comparison to full-fledged female members. Admitting women, others say, would interfere with male bonding.

"I value the male connection," said one officer. "There's a pleasure in associating with only men . . . a lot of it is borne in the easy camaraderie that I suspect would change."

That, says a member who has supported the admission of women, is "a ridiculous argument." He says current policy has damaged the club's standing and cost it members -- chiefly federal judges and public officials -- who fear the damaging publicity that could result from joining a club that bars women.

Annual dues at the exclusive club are about $600. There are currently about 100 vacancies in the club that once had waiting lists. "Younger people just don't want to get involved in this stupid fight," said one member.

Leaders on both sides agree that the question of admitting blacks was resolved far more quickly.

In 1962, columnist Carl Rowan was rejected for membership and a flurry of resignations followed. Economist John Kenneth Galbraith resigned, as did broadcast journalist Edward R. Murrow and historian Bruce Catton. President John F. Kennedy, whose nomination was then pending, withdrew his application in protest. Eleven months later the club admitted its first black member, historian John Hope Franklin, who has publicly supported the admission of women.