The 10-nation European Economic Community intends to propose an international conference this fall to try to negotiate a Soviet withdrawal from Afghanistan.

The plan, worked out by foreign ministers of the community, is expected to receive formal approval of EEC heads of government at thier meeting in Luxembourg next week and be announced then.

Among those who would be invited are the United States, the Soviet Union, Britain, France and China as permanent members of the U.N. Security Council and Pakistan, India and Iran as neighbors of Afghanistan. Representatives of the warring factions inside Afghanistan also would be invited to join in the later stages of the conference.

The complicated plan for a two-phased conference, suggested by Britain's foreign secretary, Lord Carrington, was tentatively approved by the foreign ministers of the community this week. Britain assumes the rotating presidency of the community for six months beginning July 1.

The proposal was explained to the Soviet Foreign Ministry by the British ambassador in Moscow yesterday, according to officials here. There has not yet been a Soviet response. Moscow has said previously that prospects for a political solution in Afghanistan depend on stopping alleged U.S., Pakistani and Chinese interference there. The Soviets have justified their own presence as being at the invitation of the Kabul government.

Although the Reagan administration is still awaiting the final form of the proposal, sources here said American officials have agreed with British diplomats that it is worth trying, if only to increase international diplomatic pressure for a Soviet withdrawal from Afghanistan and to test Moscow's professed willingness to negotiate a solution to the crisis.

According to the sources, the first phase of the conference, involving the five Security Council member nations, Afghanistan's neighbors and other Islamic Conference countries, would focus on the question of "external interference" in Afghanistan.

This would give the Soviets the opportunity to discuss their allegations that U.S. and other Western assistance is being given through Pakistan to Islamic rebels fighting Soviet troops and the Soviet-supported Babrak Karmal regime in Afghanistan; other nations at the conference, including the United States, would be expected to focus on the Soviet intervention.

The second phase of the conference, which would bring in representatives of the warring Afghan factions would then seek to negotiate an end to the conflict, withdrawal of Soviet troops and international guarantees of Afghan independence and neutrality. The Soviets have said that the problem cannot be solved and their troops withdrawn without involving the Afghan government.

British sources acknowledged this leaves the question of what other Afghans to invite and whether the Soviets would accept the participation of rebel leaders. "There are lots of other unresolved questions," one source said, "but the incidentals could be worked out as we go along."