Philippine senators accused the United States on Monday of short-changing Manila in a nearly billion-dollar deal for military bases and warned of possible removal of the installations after 1991.

Several hundred protesters marched on the U.S. Embassy and unfurled a banner demanding immediate closure of the United States' largest military facilities overseas. A left-wing coalition called the agreement "high treason."President Corazon Aquino declined to comment on the accord announced on Sunday, and a spokesman said it was not discussed in a 45-minute meeting she had with Adm. William Crowe, chairman of the U.S. Joint Chiefs of Staff.

Crowe told reporters after meeting Philippine military chiefs the agreement, covering compensation and other issues, would boost regional stability. He said he hoped it would pave the way for extension of the U.S. lease on the bases after it expired in September 1991.

The bases include Clark air and Subic naval facilities, manned by about 20,000 American personnel and regarded by the United States as vital to its defense interests in the Pacific and Indian Oceans.

Secretary of State George Shultz and Philippine Foreign Secretary Raul Manglapus were to sign the agreement in Washington Monday afternoon.

Manglapus said in an interview with The Associated Press the pact includes $481 million in annual payments, other U.S. concessions, an agreement on nuclear weapons and U.S. backing for a bond program aimed at reducing the Philippines' $28 billion debt.

Manila, trying to service its $28.95 billion debt, had demanded $1.2 billion annually for 1990 and 1991 against the current U.S. aid pledge of $180 million a year.