NEW YORK, NOV. 11 -- Soviet dissident Andrei Sakharov today charged the Kremlin leadership with continued violations of Soviet human rights and urged American political activists to step up pressure on Moscow to free all remaining political prisoners and further improve its rights record.

On the fifth day of a three-week trip to the United States -- his first ever to the West -- Sakharov gave speeches here to two leading political rights groups. He counseled them on the most effective methods to lobby the Kremlin on human rights issues.

On Saturday, Sakharov plans to travel to Washington, where he will attend meetings of the Foundation for the Survival and Development of Humanity, of which he is a board member, meet with President Reagan and take part in meetings with human-rights leaders.

Some of the recent actions taken by the Kremlin leadership are "very controversial and dangerous" Sakharov told an afternoon reception sponsored by the New York Academy of Sciences and the Union of Concerned Scientists.

"Many of them are a step backwards, in reality," he said.

In an earlier meeting at the New York branch of the Helsinki Watch Committee, Sakharov gave specific examples of the Soviet leadership's most serious human-rights problems, including the arrest of some political dissidents and the continued detention of others.

When the Kremlin began freeing political prisoners in February 1987, it was widely believed in Soviet and Western human-rights circles that the arrest of dissidents had ceased.

Sakharov said that such arrests have started again but added that it was not clear whether those arrested would be charged or detained for a time and then set free.

Sakharov said he considers the war in Afghanistan a major abuse of the human rights of Soviet citizens.

The Kremlin recently suspended the withdrawal of Soviet troops from Afghanistan, after removing about half of the 115,000 troops who have been fighting to sustain a Marxist regime in Kabul.

Sakharov urged American leaders to pressure the Soviets to stick to the withdrawal timetable and the Feb. 15 deadline for the total removal of troops.

He said Helsinki Watch should make the complete withdrawal of all Soviet troops and the end of Soviet involvement in Afghanistan a precondition of Western participation in a proposed Soviet-sponsored human-rights conference in Moscow in 1991.

Sakharov also charged the Kremlin with depriving Soviets of the full rights of freedom of speech.

Despite a pledge by Soviet President Mikhail Gorbachev to democratize Soviet society, some decrees are being issued and laws passed with no discussion or forewarning from the Soviet leadership, Sakharov said.

He said that despite a call by Gorbachev for more glasnost, a revision of the Soviet legal code is being conducted in total secrecy.

"No one knows what the new laws will be or even who is drafting them," he said.

Sakharov, who at 67 is in the forefront of the Soviet human rights movement, offered his view on how American activists should best exert their influence on the Kremlin.

In the past, Soviet officials have often bristled and reacted negatively to demands from the West that they strengthen their standards for human rights.

Sakharov said that the absolute release of all "prisoners of conscience," should be demanded before Westerners agree to take part in the proposed Moscow conference. The Helsinki Watch Committee estimates that 263 political prisoners are still being detained in the Soviet Union.

Sakharov suggested that Helsinki Watch maximize its pressure on Moscow to improve the plight of Soviet political prisoners by dividing the prisoners into two groups: a small group of special cases and a larger group that would include all other prisoners.

Freedom for the larger group should be demanded as an ultimatum, he said, while a more general improvement of the situation should be sought for those with special cases.

"Perestroika needs support," Sakharov told the reception attended by a group of American scientists and activists at the New York Academy of Sciences. "But that should be the support of a sober and discerning friend."

Gorbachev "should be helped" by the West in his reform drive, Sakharov added. "But he should be helped in a critical way. One should not think that all the problems {of the reforms} have been solved."

Sakharov highlighted the case of Leonid Lubman, a Russian sentenced for espionage who is currently serving a 10-year term in exile.

Calling the charges against Lubman "trumped up," Sakharov urged that the United States take up his case as a cause.

In yet another unusual development connected with the trip, several Soviet dissidents, including Sergei Kovalyov and Nikolai Chernobilsky, whose freedom to travel to this country Sakharov had championed, arrived in the United States today to participate in the foundation sessions.