Senior Defense and State Department officials expressed confidence yesterday that the change of government in the Philippines will not endanger long-term U.S. access to two strategically located military bases there.

"We're confident that any noncommunist Philippine government will see its own self-interest" in maintaining a U.S. presence at Clark Air Base and Subic Bay Naval Base even after the U.S.-Philippine base agreement expires in 1991, Navy Secretary John F. Lehman Jr. told two Senate Armed Services subcommittees.

Lehman, who termed the bases "essential" for the defense of the Philippines and Asia, said a recent Pentagon study found it would be "very costly" to relocate U.S. forces elsewhere in the Pacific. He gave no figures. "The reality is there is no substitute for Clark and Subic."

Former national security affairs adviser Robert C. McFarlane, who also testified, said it would cost $5 billion to $8 billion to build bases in the Northern Marianas islands or elsewhere, and costs of military operations from a more remote site also would be high.

Assistant Secretary of State Gaston J. Sigur Jr., who held talks in Manila last month with Philippine President Corazon Aquino and other officials, said that in view of widespread support there and in Asia for the U.S. military presence, "we have no plans to relocate our facilities from the Philippines."

Sigur added that "no one should underestimate our resolve to maintain our defense and mutual security arrangements with the Republic of the Philippines and to preserve our access to the facilities at Subic and Clark through 1991 and beyond -- with the continued cooperation and support of the Filipino people."

Former assistant secretary of state Richard C. Holbrooke, who also recently returned from Manila, said, "My guess is we will be asked to stay on [after 1991] but it will cost a lot more."

Holbrooke also said that in view of the strategic and political importance of the Philippines and a "moral obligation" assumed by President Reagan in connection with the recent Philippine elections and turnover of power, the current U.S. plan to provide $150 million in emergency aid to the Aquino government is "not enough."

Despite limits of the Gramm-Rudman-Hollings budget-balancing law, Holbrooke said the administration should consider "many other ways to increase our aid."

Aquino was quoted by the Philippine News Agency yesterday as saying she will ask voters to decide in a referendum if the U.S. forces should remain after 1991. She said the vote would come on a new bases agreement to be negotiated with the United States, but gave no timetable for either the negotiations or the referendum.

Several senators expressed concern that in the long run Soviet military forces could obtain access to Clark and Subic if the United States were forced to leave. Lehman termed such a development "the greatest worry of all."

He said that two years ago the government of Ferdinand Marcos allowed Soviet merchant ships access to repair facilities near Subic Bay. "We were not at all happy" with this action, Lehman said.