Vice President Bush today reaffirmed a strong U.S. commitment to South Korean security and brought a message from President Reagan urging continued moves toward "national reconciliation."

After a breakfast meeting with a group of dissident churchmen, journalists and scholars at which he stated the Reagan administration's commitment to human rights, he told the South Korean National Assembly that the United States sees "political diversity as a source of strength, not of weakness."

Recalling that President Chun Doo Hwan had told Reagan on his visit to Washington last year that he would work for a "freer, more abundant and democratic society" in South Korea, Bush added, "We look to President Chun and to this assembly to build on such a commitment."

Bush, on the second leg of a five-nation Asian tour, restated the Reagan admnistration pledge that the United States would keep its 37,000 troops in South Korea and indicated that the administration would reject the opening of any future talks with communist North Korea unless they involved participation by Seoul.

An embassy official called the breakfast meeting, which came amid recent signs of mounting anti-American sentiment among religious dissidents and student radicals opposed to the Chun government, as a "very free, open, useful and friendly exchange of views" on political and human rights in South Korea.

Bush told the South Korean lawmakers, "The United States has no intention of stepping aside in Korea so North Korean leader Kim Il Sung can launch another invasion and set the clock back 32 years." He suggested that the withdrawal of American troops, which had been planned by the Carter administration, would help provoke an attack by the North.

His remarks reinforced the the Reagan administration's reversal of that decision and the "unswerving commitment" to keep U.S. troops here expressed by Secretary of Defense Caspar W. Weinberger on a visit here last month.

Among those attending the meeting of dissidents at the U.S. Embassy this morning was the Rev. Pak Hyong Kyu, president of the Council of Presbyterian Churches in Korea, who, along with 41 Catholic and Protestant churchmen, signed a recent statement calling for the immediate recall of U.S. Ambassador Richard L. Walker and Gen. John A. Wickham Jr., commander of U.S. forces in South Korea, for allegedly making remarks "insulting" to the Korean people. Both men have denied such remarks.

The statement also called on the Chun government to free political prisoners and halt the alleged torture of individuals suspected of antigovernment activity.

In the background is a growing rift between the Chun government, which has asserted that such expressions contribute to North Korean propaganda efforts to discredit the Seoul government, and key activist elements of the country's large Christian minority, who have charged the Reagan administration with turning a deaf ear to responsible dissident groups.

Bush told the breakfast meeting that the United States was commited to a policy of pursuing human rights around the world through "quiet diplomacy," an apparent departure from the high public posture on the issue taken by the Carter administration.

The U.S. Embassy official expressed the Reagan administration's "concern with and interest in the welfare and conditions" of political prisoners in South Korea, including former political opposition leader Kim Dae Jung, who is now serving a 20-year prison term on charges of sedition.

Before the legislators, Bush cited the subverting of espoused democratic principles by the Sandinista government in Nicaragua and said, "The United States regrets this, just as it regrets the suppression of democratic practices in all countries, friend or foe."

In a 50-minute meeting with Chun today, Bush delivered a personal letter from Reagan. After praising Chun's moves toward national reconciliation as "most encouraging," Reagan added, "I would sincerely hope that the restoration of stability in Korea would permit the continuation of that process in the future."