Soviet Foreign Minister Eduard Shevardnadze was ordered to return home immediately to attend an urgent meeting of the Soviet Politburo, a senior Soviet official said Wednesday.

U.N. diplomats said Shevardnadze was told to leave Wednesday night for Moscow, cutting short his stay in New York, where he had been meeting with foreign ministers at the U.N. General Assembly."He is going back for an urgent meeting," Soviet Deputy Foreign Minister Vladimir Petrowsky said without elaborating.

Shevardnadze had planned to attend an important meeting of the five permanent members of the Security Council Friday to discuss the crisis in Afghanistan and hold other meetings next week.

U.N. diplomats said the urgent meeting of the Politburo may deal with threats to the Geneva accords on Afghanistan, under which Moscow must withdraw all its more than 100,000 troops by Feb. 15.

Shevardnadze hinted Tuesday that continued support for U.S.-backed guerrillas fighting the Afghan government jeopardized the completion of the Soviet withdrawal from Afghanistan.

Shevardnadze met with Chinese Foreign Minister Qichen Qian Wednesday morning and planned to meet with Democratic presidential candidate Michael Dukakis before flying home.

One diplomat said Qian is scheduled to visit the Soviet Union this year at the invitation of the Soviet government, the first such visit since the ideological split of the two Communist giants decades ago.

Tuesday, Shevardnadze followed President Reagan's lead and expressed support for an international clampdown on chemical weapons, praised the United Nations and said the entire world has benefited from improved U.S.-Soviet relations.

Shevardnadze, addressing the 159-nation U.N. General Assembly one day after Reagan gave his final speech to the international body, said the thaw in U.S.-Soviet relations has reduced the threat of war, and he credited "new political thinking" in the Kremlin for the recent cooperative spirit between the two superpowers.

In supporting Reagan's call for an international conference to strengthen the provisions of a 1925 Geneva accord outlawing chemical weapons, Shevardnadze said use of the weapons is "surreptitiously" spreading.

"The Soviet Union positively regards the proposal made yesterday by the president of the United States to convene a conference of the parties of the 1925 Geneva protocol," Shevardnadze said.

Reagan urged in his address Monday at the opening of the General Assembly's 43rd session that chemical warfare and the use of poison gas be ended "once and for all" and that existing stocks be destroyed.

Shevardnadze praised the work of the United Nations in promoting world peace.