Ronald Reagan, already making his mark as an activist president at home, finds he must now take up the role of activist diplomat abroad.
The President will try out his personal diplomatic skills in Europe June 4 to 10 - first at a Western economic summit at Versailles, then in a meeting with the Pope in Rome, and finally at a NATO summit in Brussels.
Those skills will be sorely tested. Western trading partners want relief from American interest-rate and recessionary pressures. And the problems within NATO are becoming more serious, with West Germany particularly edgy over fears of a limited-nuclear-war strategy for Western Europe.
For a White House with finely honed media instincts, the settings at the French palace outside Paris, the Vatican -- for a meeting of the two attempted assassination victims, the US President and the Pope - and the pageantry of the Brussels meeting of the alliance chiefs of state must seem rich with spectacle potential.
The trip will come after Mr. Reagan's spring domestic offensive to sell his ''new federalism'' program, and after his first round of fund raising and campaigning as head of the Republican Party. It will come before the midterm election races heat up, and before the Democrats hold their midterm convention in late June.
But there is serious work for Reagan to do abroad, however fortuitous the domestic timing.
''Active personal diplomacy may be necessary,'' says Charles F. Doran, an American foreign policy expert at Johns Hopkins University's School of Advanced International Studies. ''The purpose of the Reagan trip is to show a troubled Europe the commitment of the US to the alliance as it was.''
''Whether the President goes to Catholic or southern countries, as he will, the focus must really be on those essentially Protestant northern countries with a midroad outlook, which are shaken by the new weapons technology. Fears of a limited nuclear war have gone down to the street level.''
Some in Europe and at home would argue that the Reagan administration has delayed too long to emphasize the cohesiveness and strength of the alliance, Mr. Doran says. Europe could use a US leader's endorsement somewhat like President Kennedy's ''Ich bin ein Berliner'' speech.
''The alliance is only as strong and cohesive as is West Germany,'' says Doran. ''West Germany now lacks confidence in its external and internal politics.''
A European emphasis fits logically into the development of Reagan foreign policy, analysts here say.
The Middle East was ruled out partly because President Carter had already made so much of the region. But more important, the Reagan administration is extremely pessimistic about what to do about the Middle East. It has no policy to push forward at the moment for the President to take advantage of. Relations with Egypt and Saudi Arabia are relatively in hand. Deliveries of Middle East oil are not troubling in this period of a global oil glut.
Reagan goes to Europe after having emphasized Western Hemispheric solidarity. ''The desire to stress the strength and unity of North America distinguishes this administration from those that have emphasized the allies vs. opponents,'' says Doran. ''Reagan has not been trying to divide NATO, but to strengthen it by emphasizing North America's role - something which has been easier to do with Mexico than with Canada.''
Reagan's European visit will test whether his communications skills work as successfully with European crowds as with American.
Except for President Kennedy in Berlin, American presidents have tended not to do well with European crowds, says Doran: ''The smile, the informality, the commonness important to this electorate, do not sit well in Europe. Kennedy was looked upon as an aristocrat, which put him on a pedestal and gave him an advantage. Whether Reagan can project his charisma will be worth watching for.''
How Reagan comes across to Europeans is considered important partly because of a delicate domestic-foreign relations hand the President will have to play with the Europeans and with his own electorate in the next two or three years.
At this moment, some Reaganites are raising the threat of a possible neo-isolationism among Americans. While there is no evidence yet of domestic neo-isolationism, this argument goes, in a year or two Americans will be faced with rising military costs and sharply curbed social spending at home. If the allies are not willing to face even modest increases in alliance defense costs, Americans may sharply resent having to pay what they may perceive as more than their share.
Reagan's job will be to convince the Europeans he is sensitive to the constraints that his allies, such as West Germany's Chancellor Helmut Schmidt, are under - to emphasize the solidarity of the alliance, while also warning them it's a two-way street so far as bearing the burden of alliance defense and Soviet containment are concerned.
The European visit is also a logical prelude to an eventual Brezhnev-Reagan summit. ''The US wants to wait to deal with the Soviets from strength,'' observes Doran.
''They want to put the Soviets on warning, particularly about third-world countries,'' he says. ''They want to get the domestic house in order. They want to rebuild the military balance, while being forced by international pressure to discuss arms negotiations.''