World affairs in 1984 will continue to be overshadowed and influenced by the existence of huge Soviet and American nuclear arsenals probably capable of destroying the human race. But the danger of Soviet-American hostility triggering these arsenals may actually recede.
A minor incident at the end of 1983 gives one reason why this can happen.
The leaders of Greece and Romania joined in an appeal to their respective sponsors, the United States and the Soviet Union, to return to the bargaining table and resume efforts to reduce and restrain the nuclear danger to all.
Greece is a member of the NATO alliance. Romania is a member of the Warsaw Pact. They live on opposite sides of the Iron Curtain. But they share concern about the nuclear danger that is inherent in Soviet-American rivalry.
There is no reason to think that either NATO or the Warsaw Pact will break up during 1984. But a trend already prominent in 1983 is likely to continue and grow stronger during the year ahead. That trend is for the European clients of the two rival superpowers to push those superpowers toward accommodation rather than conflict; and for the small clients to cooperate as much as possible in that direction.
It is noteworthy in this respect that East and West Germany have not distanced themselves from each other in pace with their sponsors, but seem to be seeking closer associations. The old year ended with an almost total abandonment of any top-level dialogue between Moscow and Washington, but with many dialogues among the clients.
It is equally noteworthy that the year opens with the Chinese in the process of normalizing their relations with Moscow while continuing to be in association with the US. The prospect is that China will continue during the year ahead to adjust its relations with the two superpowers in the direction of an almost neutral position between the two.
How far the Chinese will go depends probably on the concessions Moscow might make. China wants much more than Moscow is yet willing to give. If the Soviets would withdraw from Afghanistan and diminish their support for Vietnam's expansion in Indochina, the Chinese would presumably be willing to reopen formal diplomatic relations.
If, in addition, the Soviets would reduce their armed forces along the Chinese border, the Chinese might be willing to be almost friendly. At present there are 52 Soviet divisions on the Chinese border, plus four more in Mongolia. All 56 are amply backed by nuclear weapons.
Soviet-US rivalry will continue throughout the year to be the central feature in world affairs, with both China and the Europeans working toward relative independence of the two. Both would like to distance themselves from the rivalry , while knowing there is no such thing as total escape should the two superpowers sink into war.
But might there be a break in the sense of tension that marks the US-Soviet relationship at the turn of the year?
President Reagan's rhetoric is as outspokenly anti-Soviet as ever, but he did not reimpose economic sanctions over the downing of the Korean airliner. US grain flows regularly every day to Soviet ports. A dialogue continues at lower levels.
Anything is possible during a presidential election year. If Soviet leader Yuri Andropov recovers his vigor, or if a new leader emerges in Moscow, a summit is not inconceivable. A president who goes to Peking in April is capable of going to Moscow afterward. Richard Nixon did that in 1972. It helped in his reelection landslide. Peacemaking can be a powerful political asset.
President Reagan will undoubtedly pursue his crusade against communism in Central America during 1984. He has been encouraged to press ahead by his success in Grenada and by the reaction inside Nicaragua to the pressures he has put on the regime in that country.
A tacit deal over Nicaragua is possible. If the business elements, the Roman Catholic Church, and the moderate politicians are readmitted into the power structure in Nicaragua, if the Cubans are sent home, and if aid to leftist Salvadorean rebels ceases - then Mr. Reagan could call off his own support for the right-wing rebels in Nicaragua.
El Salvador is another matter. The regime there has so far proved unable to curb the excesses of the ''death squads.'' The killing goes on. And the rebels seem to be gaining headway in the countryside. The moderate center seems to be collapsing. If it does, and if the ultraright takes over, then Congress would probably refuse more US funds. President Reagan must prevent the total collapse of the political center to save his policies in El Salvador.
The prospects are not promising.
Probably the most active and unpredictable area of the world during 1984 will be the Middle East. Israel is for the first time in its history overextended. Its government cannot afford to keep its armed forces on a war footing and inside southern Lebanon much longer, even with increased US subsidies. But a full withdrawal of Israeli forces from Lebanon would be a politically damaging admission that the 1982 invasion of Lebanon was largely in vain.
US marines are in an equally unfavorable position just south of Beirut. They went in as a peacekeeping force and have become partisans in a virtual civil war. They are in frequent combat with the militia forces of both the Druze and Shiite factions. And their military position is almost untenable.
According to conservative and influential Republican columnist William Buckley, it is time for Mr. Reagan to get the marines and the US out of the smoldering feuds of Lebanon. Sen. Barry Goldwater of Arizona says the same.
So do most other Republican leaders in Congress. So do most Democrats.
A year ago the US was in the position of being able to mediate between Israel and the Arabs. Today it is more committed to Israel, hence less regarded by the Arabs as a mediator.
A withdrawal of the marines would leave Syria in virtually undisputed control of most of Lebanon. Lebanese President Amin Gemayel would have to become a client of Syria to expand his control beyond Beirut and its immediate suburbs.
No outsider can foresee how Syria will play its much stronger hand in the area. The only certainty is that Syria is in a strong position and will be even stronger if and when the US marines are withdrawn. King Hussein of Jordan would like to get into talks with Israel about the West Bank. And Israel may be willing to think in terms of an agreement with him on that subject. But King Hussein will be reluctant to move without the approval of Syria.
Such matters will deeply concern both White House and Kremlin during 1984.
But the biggest concern must be growing world awareness of the awesome danger of something setting off a nuclear war. As the year opens, formal talks about such matters have been suspended. The biggest challenge for all governments is to get such talks reopened and headed in a constructive direction.
There is virtually general agreement that the nuclear arsenals must be brought down to reasonable levels. Can 1984 make a start in that direction?