WASHINGTON (AP) _ The federal government wants to break Burroughs Wellcome Corp.'s monopoly on the AIDS-fighting drug AZT and encourage price-lowering competition.

The National Cancer Institute should be named co-inventor of AZT with Burroughs Wellcome, now the only U.S. source of the drug, Dr. Bernadine Healy, director of the National Institutes of Health, said Tuesday.

Healy said the government and the company do not disagree significantly about the nature of their scientific contributions to the development of AZT, but they do about the patent law consequences.

Burroughs Wellcome holds a patent on the use of AZT to treat AIDS, giving it a legal monopoly on supply of the drug.

''NIH believes that investigators at the National Cancer Institute should have been named as co-inventors on the AZT-related patents issued to Burroughs Wellcome,'' she said in a statement outlining NIH's claim to AZT.

That would enable the National Institutes of Health to license other companies to produce the drug.

Two lawsuits have set the stage for legal resolution of the issue. One was filed in March by the People with AIDS Health Group and several AIDS patients challenging the validity of Burroughs Wellcome's AZT patents.

The company has filed a motion to dismiss the suit, as has the government, which is named as a co-defendant.

In another case, Barr Laboratories Inc. of Pomona, N.Y., is challenging the validity of the patents. Barr has submitted an application to the Food and Drug Administration seeking to market AZT for treatment of people infected with HIV, the AIDS virus, but who have no symptoms.

Barr also has requested a license from NIH ''to the extent that NIH may have rights in Burroughs Wellcome's AZT patents.''

''NIH is contemplating the granting of this license so that the company legally would be able to market AZT if it is ultimately determined, in litigation between Barr and Burroughs Wellcome, that the government is entitled to inventorship status,'' Healy said.

''In that event, competition would result in a lower price for AZT,'' she said.

AZT treatment currently costs about $3,000 a year. The price could be cut by one-half to two-thirds if made as a generic drug without patent protection.

Burroughs Wellcome maintains that its scientists were the first to conceive of the use of AZT for the treatment of HIV infection ''and this creative insight is the basis for the use patent granted in 1988,'' said Kathy Bartlett, a company spokeswoman.

''The company has acknowledged the collaborative efforts, but this doesn't require the collaborators to be named as co-inventors,'' she said.

AZT was discovered under an NCI grant in the 1960s. When scientists were searching for antiviral compounds to fight the AIDS virus in the mid-1980s, AZT was pulled off the shelf as a possibility.

Healy said NCI scientists applied state-of-the-art laboratory analysis to AZT in early 1985 to evaluate its possible therapeutic value and helped develop an understanding of the AIDS disease process.

''NCI was the most appropriate research collaborator for Burroughs Wellcome for these reasons,'' she said.

Though AZT was already in the public domain when the AIDS epidemic took root, ''the intellectual and scientific contributions made by NCI to the evaluation of AZT were essential components of the invention of AZT therapy for AIDS,'' Healy said.