A top California Republican has broken party ranks on the controversial issue of offshore oil drilling in that state, warning Interior Secretary James G. Watt that opening up contested areas to leasing would be "a 'no win' situation" that could hurt candidates in next year's elections.

In a June 1 letter, made public by an aide to Sen. Alan Cranston (D-Calif.), state GOP chairman Tirso del Junco urged Watt to postpone leasing four tracts off scenic parts of northern California until 1983 and to put the controversial tracts in the Santa Maria basin off San Luis Obispo into a new kind of strategic petroleum reserve rather than drilling.

Otherwise, del Junco wrote, "the progress we [GOP politicians] are making now can be severely hampered should our candidates be forced into supporting the decisions which you have made" to push oil leasing.

Watt has not formally decided to offer the northern areas for leasing, and a decision to lease 32 tracts in the Santa Maria basin is stalled by a lawsuit against it filed by Gov. Jerry Brown, a Democrat.

"The issue of offshore oil drilling leases is one which I feel has not been explained clearly to the public. And the public's reaction has been based on perhaps misguided fears of damage to the coastal waters and wildlife," del Junco wrote. "Whether that perception is right or wrong, it does exist."

He added that while he supports many of Watt's decisions, "I believe it should be recognized that the Santa Maria oil lease sale is, in all cases, a 'no win' situation and that some method of compromise should be sought as quickly as possible."

Rep. Don Clausen (R-Calif.), whose district includes three of the four northern sites, said he had suggested the petroleum reserve concept and was "pleased to have that support" for it. He agreed that the leasing issue was "subject to all sorts of political exploitation."