The Veterans Administration was warned yesterday that unless it starts a pilot project on the health effects of Agent Orange within a month, legislation will be introduced to turn the project over to the federal Centers for Disease Control.

The warning came from Rep. Thomas A. Daschle (D-S.D.) as a House Veterans Affairs subcommittee opened hearings on the VA's progress on the project.

VA officials recently said that it would probably take until 1988 or 1989 to complete a study comparing veterans who might have been exposed to the defoliant while serving in Vietnam to those who were not exposed.

In the meantime, the VA said, veterans cannot be compensated for disabilities attributed to Agent Orange because research has not established that the ailments are service-connected.

Several lawmakers said that Congress may decide, without waiting for the research, to compensate veterans for certain disabilities, even if evidence is lacking that they were caused by Agent Orange.

Rep. Margaret Heckler (R-Mass.) said $5 million on Agent Orange out of a $140 million research budget "is an incredibly small amount."

Daschle accused the VA of "bureaucratic and bungling delays." Rep. Bob Edgar (D-Pa.) said the VA had been reluctant to act "until we hit them over the head with a two-by-four."

Dr. Donald L. Custis, chief of the VA's department of medicine and surgery, denied that the agency was purposefully delaying the studies.