The Reagan administration yesterday urged the Supreme Court to overturn its 1973 decision legalizing abortion, arguing that there is no constitutional right to the procedure.

The Justice Department, in a brief approved by President Reagan, said the court's landmark decision in Roe v. Wade was "inherently unworkable," and "so far flawed that this court should overrule it."

The unusual move was immediately hailed by antiabortion groups and condemned by "pro-choice" organizations. But both sides agreed there was little chance that the justices, who voted, 6 to 3, two years ago to reaffirm a woman's "fundamental right" to abortion, would overturn the 7-to-2 Roe ruling.

The department two years ago stopped short of asking the justices to overrule the 1973 decision, asking instead that the court allow the states greater leeway in regulating abortion.

However, yesterday's "friend of the court" brief, filed in two cases essentially similar to those decided in 1983, strongly urged the court to "return the law to the condition in which it was before that 1973 case was decided."

Sources familiar with the administration's decision to go further this time, despite the defeat two years ago, said there was little dispute in the department to the move.

The different strategies, according to knowledgeable sources, may reflect different styles between former attorney general William French Smith and current Attorney General Edwin Meese III, who is expected to be markedly more activist in advocating administration views.

The decisions also reflect a shift in philosophy from that of the more pragmatic former solicitor general Rex E. Lee. Lee said yesterday, however, that the approach taken two years ago did not mean that yesterday's action "was not a good idea at this time."

In the 1973 decision, the high court divided pregnancy into three stages, or trimesters, and said that during the first third the decision on abortion must be left to a woman and her doctor. During the second trimester a state may pass laws designed to protect a woman's health. States generally may restrict abortions and take steps to protect a fetus only in the third trimester, when a fetus is "viable" or able to live outside the womb.

In its brief, filed by acting solicitor general Charles Fried, the department said the states had "a legitimate interest" in regulating abortion and that federal appeals courts were wrong in striking down laws in Illinois and Pennsylvania.

Technological and medical advances have made the trimester lines "unworkable" and the 1973 decision's framework has "no moorings in the test of our Constitution or in familiar constitutional doctrine," the brief said.

The appeals court's approach to state regulations, the department said, "betrays in our view an extreme and unseemly hostility to legitimate state regulation of abortion . . . . The courts seemed determined to make regulations so difficult to sustain that abortions before the third trimester will become available virtually on demand."

Pennsylvania's law required that abortions be delayed for a 24-hour waiting period, that doctors detail the detrimental effects of abortion and that abortions preformed after the first trimester be performed in a hospital.

The Illinois law threatened doctors with criminal prosecution if they fail to use the abortion method most likely to preserve the life of the fetus when there is a "reasonable possibility of sustained survival" outside the womb.

Douglas Johnson, legislative director of the National Right to Life Committee, praised the administration for taking a "small but important step" but said it was unlikely the "current Supreme Court" would overturn the 1973 ruling.

David Andrews of Planned Parenthood of America called the filing a "blatantly political move on the part of the Reagan administration to appease antiabortion elements," and said the administration wanted a "return to the days of illegal and dangerous 'back-alley' abortions."

Judy Goldsmith, president of the National Organization for Women, called the brief "unconscionable and prefectly predictable. This is an all-out assault on women's rights to make their own reproductive decisions and instead have the government make those decisions for them. It is a continuation of the Reagan administration's war on women."