MANILA, Philippines (AP) _ Communist rebels marked their party's 19th anniversary Saturday with their first-ever radio broadcast and said they were nearing a stalemate with President Corazon Aquino's 22-month-old government.

Philippine reporters who heard the broadcast said the station, calling itself ''Radio Sierra Madre, Voice of the Free Philippines,'' broadcast about 9 p.m. for about a half hour in the Pilipino language over an unused FM frequency.

A select audience, including some reporters, was tipped off in advance to tune in to the broadcast by the clandestine Communist Party of the Philippines.

''The people's war is now nearing the stage of strategic stalemate,'' the male announcer said.

The party's military arm, the New People's Army, has 23,000 members and has been fighting a guerrilla war against Mrs. Aquino's government for 18 years.

The program said Mrs. Aquino failed to address the debt-strapped country's problems and her government's human rights record since she was swept to power in a February 1986 military-civilian uprising that toppled President Ferdinand Marcos.

It also accused the United States of meddling in Philippine domestic affairs and citied the mushrooming of anti-communist vigilante groups nationwide.

It played revolutionary songs and sent fraternal greetings to Cuba, which celebrates its 29th anniversary Dec. 31.

The Sierra Madre is a mountain range north of Manila that has been a longtime rebel stronghold, but it was not known whether the transmitter was there.

The Maoist party, with a handful of university ideologues and peasants, broke off from the pro-Soviet Partido Komunista ng Pilipinas on Dec. 26, 1968, accusing it of degenerating into a band of smugglers and thieves.

Three months later the party created the New People's Army.