Charito Planas, an outspoken critic of Philippine President Ferdinand Marcos, has arrived in the United States after what she described as almost two months of hiding in locked rooms, traveling in disguise, and narrowly evading soldiers and police.

The dissident lawyer appeared in Washington yesterday at a press conference where she denounced the Marcos government as "repressive" and urged a halt to U.S. aid to the Philippines. Planas, who had gone into hiding April 7, was sought by Philippine authorities on subversion charges. She said she reached the United States Monday.

Planas' difficulites with the government were discussed when Vice President Mondale met with prominent Filipino dissidents in May, and Planas credited Mondale yesterday with making possible her escape from the Philippines by offering her asylum in the United States.

Albert Eisele, Mondale's press secretary, declined to confirm Planas' assertion yesterday, saying, "I could not go into the details of it since it was a private meeting."

In an interview after her news conference, Planas, 45, recounted some episodes of her escape from the Philippines. On several occasions in May, she said, she came "face-to-face" with Philippine soldiers but was not recognized because of her disguise. She refused to disclose many details, however, saying she wanted to avoid endangering those who helped her escape.

She said she had been kept hidden by friends and political sympathizers at five separate locations in the Manila area, often remaining silent in locked rooms for days at a time to avoid detection.

She made her getaway from the Philippines May 18, Planas said, but she refused to say how she traveled or where she went. Other sources have reported that she went by boat to Malaysia, from which she later departed by airplane. A State Department spokesman said yesterday that Planas had eventually gotten in touch with the U.S. embassy while she was in Kuala Lampur, the Malaysian capital.

Planas ran as a candidate on an anti-Marcos slate for a new, interim National Assembly in April. The entire dissident ticket was defeated in the election, which was marked by charges of voting irregularities and widespread arrests. Planas received nearly one-third of about 3.1 million votes cast in Manila.

Planas was imprisoned for 14 months in 1972 and 1973, when Marcos first imposed martial law but she was later released and permitted to campaign vigorously against the president.

Planas arrival in the United States had been expected to further irritate U.S.-Philippine relations, which have been strained by American criticism of allaged Phillipine human rights violations and by continuing negotiations over two major U.S. military installations in the Phillippines.

State Department spokesman Jack Cannon said yesterday, however, that Planas' arrival here would not affect U.S. Philippine relations. She has been admitted to the United States as a parolee, an emergency immigration procedure, and is expected to apply for asylum later. The Philippine Embassy issued a statement describing Planas as a "fugitive from justice" who, it said, has had ties with Communists and terrorists.

Planas went into hiding after a police raid on her home in Quezon City, on the eastern outskirts of Manila. She said yesterday that she had returned after the April 7 elections to find her house surrounded by solders.

The government later announced that a .30-caliber rifle, ammunition and "subversive documents" had been found during a search of her home. Planas asserted yesterday that these had been "planted" by Philippine authorities.

During yesterday's news conference, Planas' voice broke and her eyes filled with tears as she said. "I have to bring back our own lost freedom." She has been named director of political refugee affairs of the Movement for a Free Philippines, an anti-Marcos group here.