Three women pleaded guilty in federal court in Washington yesterday to participating in a conspiracy that planned and carried out the Nov. 7, 1983, bombing of the U.S. Capitol, an act that they said was a protest of the U.S. invasion of Grenada.

The women's plea agreement with the government, which came more than two years after they were indicted, clears the way for prosecutors to drop charges against three other defendants, including longtime antiwar activist Alan Berkman, who is being treated at D.C. General Hospital for a recurrence of Hodgkin's disease.

Two of the women, Laura Whitehorn and Linda Evans, both 43, used similar language in court to say they were "guilty of participating in a conspiracy . . . to resist and protest the unjust practices of the United States." Marilyn Buck, also 43, answered "Yes, I am," when U.S. District Judge Harold H. Greene asked if she was guilty of the charges against her. All three were held without bond for sentencing on Nov. 28.

The hearing attracted scores of the women's supporters, and they demonstrated outside the courthouse afterward.

The conspiracy included the bombing of the National War College at Fort McNair on April 26, 1983, the bombing of the Washington Navy Yard computer center on Aug. 18, 1983, and the bombing of the officers club there on April 20, 1984, along with four other East Coast bombings.

In addition to the conspiracy count, the three pleaded guilty to bombing the Capitol. According to the government's statement of facts, the evidence against the women showed their involvement in the making of the bomb. But the government provided no evidence that the three actually planted the bomb.