Clark Air Base in the Philippines is of questionable future value unless the United States intends to maintain "a capability to mount and support major military operations on the Southeast Asian mainland," according to a Senate staff report.

The report on U.S. Philippine negotiations over military bases urges that the administration review its policy objectives in Asia and the available alternatives to bases in the Philippines to prepare a negotiating strategy.

At the request of the Philippines, negotiations on a new base agreement formally opened a year ago.

The report to Sen. Hubert H. Humphrey's Subcommittee on Foreign Assistance raises questions about a Ford administration study before the negotiations which concluded that U.S. retention of "all facilities and functions" in the Philippines was vital to U.S. objectives in the Pacific.

It calls Subic Naval Base and the adjacent Cubi Naval Air Station the most important U.S. facilities in the Philippines, bringing considerable dollar savings as well as strategic advantages.

But, the report by subcommittee staff director Robert Mantel says the importance of Clark Air Base cannot be accurately gauged in the absence of a policy reassessment for the area.

Clark covers 130,000 acres, more than three times the size of the District of Columbia, which covers 39,680 acres.

The key outstanding issues between Washington and Manila where the base negotiations entered a lull last October were: the size of the U.S. quid pro quo for continued use of the bases, the nature of Philippine sovereignty over the bases and the extent of the U.S. defense commitment to the Philippines, according to the report.

A mysterious episode last December clouded the negotiating picture. State Department officials told Congress that then Secretary of State Henry A. Kissinger and Philippine Foreign Minister Carlos Romulo had met in Mexico City and reached an agreement in principle that would be announced jointly.

The terms included a $1 billion U.S. payment in return for use of the bases for five years, half in grant military aid and sales credits and half in economic aid.

However, Romulo denied that an agreement had been reached and the Philippine government stated it wanted $1 billion in military aid alone with an unspecified amount of economic assistance.

It is not clear whether Kissinger thought he had an agreement and did not or whether Romulo had agreed without having President Ferdinand Marcos' approval.

The Senate staff report notes the long and close U.S. - Philippine relationship, which has created both good will toward the United States and some resentment because of the widespread American economic and cultural influence in the Philippines.

Marcos declared martial law in September, 1972, and the human rights situation in the Philippines is disturbing, the report says, particularly since the Philippines was an American colony.

The State Department has reported torture and degrading treatment of political prisoners, but the number appears to be declining, the report says.

It also notes that official corruption continues with the beneficiaries. The report does not go into detail, but a visitor to the Philippines soon hears tales of kickbacks and other squeezes demanded by the president and his family whose wealth is reportedly stupendous.