President Reagan today opened three days of talks with world leaders, attempting to counter a Soviet propaganda blitz with a planned initiative aimed at resolving U.S.-Soviet conflicts in international trouble spots, including Afghanistan and Nicaragua, administration sources said.

In an attempt to shift the focus of U.S.-Soviet relations away from arms control, Reagan is expected to call for Soviet disengagement in these countries when he speaks Thursday to the U.N. General Assembly in the midst of ceremonies celebrating the 40th anniversary of the founding of the United Nations.

His proposal is expected to include a call for superpower involvement in resolving these regional conflicts. Tonight, at a reception Reagan hosted for world leaders, the president agreed to meet with Soviet Foreign Minister Eduard Shevardnadze for a half-hour on Thursday to discuss the U.S. initiative and the forthcoming superpower summit.

Reagan offered a partial preview of his Thursday speech in written answers to questions posed by The Times of India and made public today. The speech has been described by White House officials as the opening volley in the president's effort to recapture the public-relations initiative in the four weeks before his summit meeting with Soviet leader Mikhail Gorbachev Nov. 19-20.

Reagan's meetings today with India's Prime Minister Rajiv Gandhi, Pakistan's President Mohammed Zia ul-Haq and Britain's Prime Minister Margaret Thatcher kicked off three days of consultations with allies, a high point of which will be a "mini-summit" of six leading industrial democracies Thursday. Administration officials have described the U.S. effort here as a dress rehearsal for the Geneva summit.

In his newspaper interview, Reagan said he will ask Gorbachev to withdraw the more than 100,000 Soviet troops in Afghanistan and restore the country's independence and nonalignment.

"It's clear that the Afghan spirit of independence cannot be crushed, that continued war will only mean more bloodshed and that only a political solution is possible," Reagan said in the interview. "The Soviets claim that they, too, believe in a negotiated settlement. I know the Soviet Union has concerns about the countries on its border, but Afghanistan poses no threat to its security."

Referring to regional conflicts stemming from the "imposition" of Marxist-Leninist regimes over the last decade, Reagan said these governments are often "at war with their neighbors" and represent "a pattern that has to be broken."

"The Soviet Union, as we see it, is too often supporting, and sometimes directing, these wars. In such cases, the flow of arms from outside is a major concern, and we want to do something about it," he said.

Although Reagan did not identify the nations he was talking about, his initiative is apparently aimed at conflicts such as those in Nicaragua and Afghanistan, where U.S.-supported rebels are opposing Soviet-supported regimes.

White House officials provided sketchy details of Reagan's plan today, in the hope that the president's speech will get maximum exposure when delivered Thursday before an audience expected to include at least 80 world leaders and Soviet Foreign Minister Shevardnadze. Presidential spokesman Larry Speakes said Reagan would propose a "broad, far-reaching initiative" that he hoped would produce a Soviet response.

Reagan, whose administration has often been critical of the United Nations, said at a luncheon honoring the institution that "we've never stopped taking the United Nations seriously."

The president's desire to shift attention from the Soviet arms proposal on reducing nuclear weapons to regional issues was expressed repeatedly today. Thatcher and Reagan voiced concern about "the amount of publicity given the Soviet proposal as if there were no U.S. proposal," a senior U.S. official said. Both leaders also agreed on the need to show that the superpowers' relationship is "broader than arms control," the official said.