A cautious mood of optimism emerged from the European summit here that Moscow might at long last be willing to withdraw its 85,000 troops from Afghanistan in return for guarantees for Afghan neutrality. "There's a chance we might be able to do it," said British Foreign Secretary Lord Carrington June 30 as he prepared to fly to Moscow July 6 to explain a new European plan for a two-stage international conference to Soviet Foreign Minister Andrei Gromyko.
Lord Carrington, nothing if not a realist, emphasized the word "chance." He offered two reasons: The Russians were in military and other difficulties in Afghanistan, and their invasion of an Islamic, nonaligned country had proved exceedingly unpopular in the third world.
Other sources here saw additional possible reasons: Faced with major problems in Poland, continued hostility from China, and a tough-sounding Reagan administration in Washington, the Soviets may now want to ease one area in which it is making little military headway.
Eventual success for the new plan, adopted by the summit here after being proposed by Britain, remains highly uncertain, however.
The Soviets are unlikely to accept any agreement that would take Afghanistan out of Soviet control. The Kremlin sees the only threat to Afghanistan coming from outside: expecially from Pakistan, the United States, and China. Soviet leader Leonid Brezhnev has twice this year said the Soviets are willing to hold talks to end external aggression and ensure it cannot happen again.
Lord Carrington himself acknowledged his plan was not the solution the Russians would have chosen. He seemed heartened by the fact that Moscow had not rejected the plan out of hand June 23 when it was first explained by the British ambassador in Moscow.
He also made it clear he had prepared the ground carefully with all planned participants in the talks. It was understood here the United States was willing to see the plan go ahead.
The first stage of the plan would bring together the five permanent members of the United Nations Security Council -- the US, the USSR, China, France, and Britain -- plus India, Pakistan, Iran, and the secretaries-general of the United Nations and of the Islamic Conference.
London has checked with all these countries. China and France promptly assented. Pakistan was favorable, the Indians somewhat less so.
Although the Soviets simply ignored the most recent proposal for a conference (from France some months ago), it is thought here that they are at least considering the new plan, which is endorsed by 10 European countries and others.
Now Lord Carrington, president of the European Council for six months from July 1, is pursuing Soviet views at the Politburo level.
The second stage of the new plan would bring in "representatives of the Afghan people." The name of Babrak Karmal, the leader installed by the Soviets during the invasion of December 1979, is not mentioned but implied.
The plan is deliberately vague on such details as where the conference would be held and who would chair it. A special statement by the European summit, endorsing the plan, suggests October or November as possible dates.
Thus, the Soviet Union would have one more reason not to invade Poland: If it did, the new proposal would be withdrawn.
British Prime Minister Margaret Thatcher said June 30 that if the Russians did want to withdraw from Afghanistan and return the nation to its previous status, the plan would give it a chance. If not, then the West would "utterly condemn Soviet actions."