The major Western European powers are now prepared to push both the United States and the Soviet Union toward acceptance of their plan for a neutralized Afghanistan without Soviet troops.

The Common Market proposal essentially calls for a guarantee of Afghan neutrality to be made following the withdrawal of Soviet troops. Sources here say that British diplomats believe that would have to include an end to reported CIA support for the Afghan rebels as well as a halt in financial support from conservative Islamic states.

According to British sources, the Europeans have detected signs of interest in their proposal from both superpowers and intend to submit their proposal, on behalf of the common Market countries, to the Soviet Union "within a few days."

The impasse between the superpowers over Afghanistan involves both elements of the plan, with the Soviets having expressed unwillingness to remove their troops as long as the insurgency against the government in Kabul continues, and with the United States demanding the Soviet troops' withdrawal as a precondition to any other steps.

The Europeans have described the U.S. approach as one-dimensional and confrontational, while the countries of the European Economic Community have arrived at a two-pronged policy of seeking a negotiated solution with the Soviets while strengthening Western ties with countries around Afghanistan to contain the Soviets if they refuse to negotiate.

European diplomats are studying closely what could be a series of signals from Moscow of Soviet interest in Afghan Neutrality.

In a nationwide television address last week and a meeting with businessman Armand Hammer in Moscow yesterday, Soviet President Leonid Brezhnev discussed guarantees the Soviets were seeking that what he termed outside interference in Afghanistan would cease. In addition, the London Evening News yesterday carried a report believed to emanate from influential Soviet journalist Victor Louis in Moscow that the Soviets are making "authoritative soundings aimed in Lord Carrington's direction."

Lord Carrington, the British foreign secretary, suggested the plan last week and it was unanimously adopted by the other EEC foreign ministers at a meeting in Rome.

Because Italy currently holds the EEC presidency, sources here expect Italian diplomats to make contact with Soviet diplomats on the plan in Rome or Moscow.

Officials here and in other European capitals also have welcomed what they interpret as American support for the plan in a letter President Carter sent to Yugoslav President Tito and comments by Secretary of State Cyrus Vance after meeting with the foreign ministers of Australia and New Zealand in Washington yesterday. Vance was briefed on the European proposal last week in individual consultations with European foreign ministers in London, Bonn, Paris and Rome.

The plan is expected to be explored further with Carter by West German Chancellor Helmut Schmidt when they meet in Washington next week. After a flurry of consultations among the European allies this week, Schmidt also is expected to discuss with Carter the rest of a coordinated European policy on the Afghan crisis.

Many details still have to be worked out by the Europeans, who still disagree over some specifics including what to do about next summer's Olympic Games in Moscow. The British government publicly has asked its athletes to boycott the games, and sources here said several other Western European countries including West Germany are ready to do the same.

But France continues to oppose an Olympic boycott, and most of the others -- again including West Germany -- want to wait as long as possible before declaring themselves to see if the Soviets make concrete moves toward negotiation of a withdrawal from Afghanistan.

British officials also expect their national Olympic committee to defy the government and vote next week to accept its invitation to the games. Other European Olympic committees are expected to delay until nearer to the International Olympic Committee deadline in May for a decision on attending the games.

However, the nine EEC countries -- Britain, West Germany, France, Italy, Ireland, Denmark, Belgium, the Netherlands and Luxembourg -- agree on the Afghan neutrality proposal. Even French President Valery Giscard d'Estaing publicly supported it at a Paris press conference this week.

Although specifics and a mechanism for negotiating with the Soviets are still being worked on, British diplomats are seeking a way for the West and the Soviet Union to agree on a Soviet withdrawal that would leave Afghans free to choose their own nonaligned government, but not necessarily through elections.In return, the West would ensure that military and economic aid to Moslem rebels in Afghanistan was stopped and that no Western nation nor any of the countries around Afghanistan would threaten its neutrality.

British sources said the Afghan neutrality plan also will be discussed in detail with those countries, particularly Pakistan, where some of the Moslem Afghan rebels fighting the Soviet troops are based.

The London Evening News report said Carrington was being signaled by the Soviets that "even the stationing of United Nations troops in Afghanistan would not be objected to by Russia, provided the terms were right and they lead to a free election of a regime representative of the people."

British officials said they have received no direct communications along these lines from the Soviet Union, but believed the report was another one of the trial balloons from the Kremlin that the well-connected Louis, Moscow correspondent of the Evening News, periodically floats in the newspaper.

European diplomats believe it is important to find a way for the Soviets to save face while withdrawing their troops, something that an American Ultimatum and diplomatic and economic retaliation against the Soviet Union had not offered.