The Soviet Union has indefinitely suspended the withdrawal of its remaining 50,000 troops from Afghanistan because of the country's deteriorating political and military situation, a foreign ministry official said Friday.

Deputy Foreign Minister Alexander Bessmertnykh said Moscow will resume the pullout when the United States and Pakistan, which supply and aid Afghan rebels fighting the Soviet-backed government in Kabul, stop violating the Geneva peace accords.He admitted Soviet bombers were being used in strikes against Afghan rebel positions but denied, as the United States claims, that the raids were offensive in nature and in violation of the April peace pact. Washington has issued a formal complaint to the Kremlin about the bombings and the introduction of long-range Scud-B missiles into the country.

Bessmertnykh said that even though the Kremlin would like to complete the pullout of its troops by the Feb. 15 date specified in the Geneva peace pact, continued Islamic rebel attacks, an unstable political situation and increased arms supplies to the Afghan rebels may keep the deadline from being met.

"For the time being by virtue of the military and political situation which I have referred to, the withdrawal of the troops is being suspended," Bessmertnykh said.

In Chicago, President Reagan said, "I think we're all disappointed," but noted, "They said they're still abiding" by the Geneva accords. Earlier, White House spokesman Marlin Fitzwater said the suspension "can only increase tensions in the region and raise speculation that they aren't going to live up to the Geneva accords."

In Pakistan, Sayeed Ahmed Gailani, head of the rebel National Islamic Front of Afghanistan, said, "We always had doubts about Russian sincerity in this regard, so it's not a surprise. But we have become much stronger lately, and if the Soviets don't go willingly we can persuade them" by force.

Another Afghan leader, Sigbatullah Mojadidi, said, "We don't care, because we have never stopped fighting as a result of the Geneva accords or the withdrawal of Soviet troops."

Bessmertnykh said the pullout must be honorable and one that does not leave the impression rebel guns were forcing the Soviets out of an occupation that Soviet leader Mikhail Gorbachev has referred to as a "bleeding wound."

"What is important is not the date itself when this withdrawal will be continued. What is important is the date by which this withdrawal will be completed," Bessmertnykh said.

"The Soviet troops are being withdrawn from Afghanistan due to the goodwill of the Soviet government and they will be withdrawn in honorable conditions. Those are not the conditions which the opposition is trying to impose on us. They do not provide such conditions for the withdrawal of Soviet troops," he said.

"The Soviet Union intends to stand by its obligations on the Geneva accords. For these provisions to be fulfilled, all countries should comply with their obligations. If it is the case that all parties to the agreement do not violate the accord, the obligations will be observed by the Soviet Union," Bessmertnykh said.

Fresh combat troops are being rotated into the country to replace units who have completed their tours of duty, Bessmertnykh said.