President Corazon Aquino on Tuesday welcomed the "substantial improvement" in U.S. compensation for the use of two strategic military bases, putting the best face on an agreement condemned as a sellout by her political opponents.

The agreement, signed Monday afternoon in Washington after more than six months of talks, "reaffirms the enduring bilateral relationship between our respective countries and allows us to proceed to improve other aspects of that relationship," Aquino said in a statement released by her press secretary."A definite and substantial improvement was obtained over the old compensation terms" for the use of Clark Air Base and Subic Bay Naval Base, America's largest foreign installations, the statement said.

The deal provides for $481 million a year in military and economic aid in the last two years of the Military Bases Agreement, which expires in 1991. It represented a substantial increase from U.S. compensation of $180 million a year under the previous five-year pact but falls short of initial Philippine demands for $1.2 billion a year.

Other major changes in the pact announced Tuesday specify that the Philippines will acquire title to all permanent buildings and structures on the bases and acquire the right to approve the storage and installation of nuclear weapons in the country.

Despite the improvements, there was widespread dismay in Manila at the agreement, which was signed by Philippine Foreign Secretary Raul Manglapus and U.S. Secretary of State George Shultz.

"We asked for 12 boxes of apples and they gave four bags of peanuts," said Sen. Ernesto Maceda, reflecting the mood in the Senate, the country's treaty ratifying body. "Our need for money boxed us into a corner," Maceda said.

"We will have to make the best of what's available," said Defense Secretary Fidel Ramos. "There's never really enough, is there?"

Officials said the interim agreement does not need Senate approval, but any new agreement to replace the basic pact will have to pass through the upper house.

The Senate last June approved a tough anti-nuclear bill that awaits action by the House of Representatives.

Washington has a policy of neither confirming nor denying the presence of nuclear weapons at its facilities. U.S. officials have said it would be extremely difficult for the United States to operate Clark and Subic if the nuclear-free provisions in the Philippine constitution are implemented.

The agreement in Washington did not address Philippine Senate concerns over the nuclear issue. For the next two years at least the status quo remains.

Militant leftist groups denounced the agreement as a "sellout of national sovereignty" and demanded the immediate dismantling of Clark and Subic, which host 17,000 military personnel plus dependents.

Sen. John Osmena, a pro-bases advocate, said Washington has failed to appreciate the nation's heavy foreign debt of $28 billion. He said economic problems were fueling the 19-year-old communist insurgency.

"The bases have no use to the Americans if the insurgency is not overcome. In this sense, the American government is pennywise and pound foolish," Osmena said.