The Soviet Union's requirements for withdrawing its troops from Afghanistan remain centered on regional guarantees against alleged outside aggression there and assurances of Soviet border security, visiting West German ex-chancellor Willy Brandt was told today by top Kremlin officials.

Brandt met for three hours with nonvoting Politburo member Boris Ponomaryov and Central Committee foreign affairs specialist Vadim Zagladin, a spokesman for Brandt said.

The spokesman said the Soviets asserted Moscow would view as acceptable a negotiated settlement which barred all intervention in Afghanistan from Iranian and Pakistani territory, and assured Kabul's "nonaligned" status. Conbined with guarantees for Soviet frontier security with Afghanistan, the Soviets would then withdraw their troops, "gladly," Ponomaryov was reported to have said.

As outlined by Brandt's spokesman, the Kremlin's position on its intervention has not changed and is virtually identical to proposals made in May 1980 by the government of Babrak Karmal, which remains in power on the strength of about 85,000 Soviet troops battling Moslem insurgents.

Meanwhile, the official Tass news agency, in a Washington dispatch, denounced the European Common Market's latest initiative for a negotiated settlement as flawed because it would exclude the Babrak government from the first round of talks. The British foreign secretary, Lord Carrington, is due here Sunday to lay out the European Community position in top-level talks next week. The plan would start with a conference of Britian, China, France, the United States, the U.S.S.R., Inda, Pakistan and Iran to agree on safeguards for Afghan security.

The second stage would include Afghan representatives. But the initiative is given scant hope of being acceptable to Moscow in that form, since the second stage leaves open the question of who the Afghan representatives would be.

Tass said the European proposal was welcomed by U.S. Secretary of State Alexander M. Haig Jr. because it is "actually directed at excluding the main and basic side -- the government of the Democratic Republic of Afghanistan -- form a quest for a settlement of the "Afghan problem."

Moscow views the Kabul proposals of last year "in the context of normalization of the situation of the region as a whole," Tass added, and wants a regional settlement as well, "in linkage with questions [about] the security of the Persian Gulf. Naturally, only the international aspects of the Afghan problem can be discussed."