WHEN George Bush arrives in Costa Rica tomorrow for the first ``summit of the Americas'' since 1967, observers will watch one encounter very closely: Will he have to smile and shake hands with Sandinista chief Daniel Ortega? It's not strictly a question of ceremony.
During the Reagan years, Mr. Ortega and his leftist regime in Nicaragua were prime targets for the United States - and the dominant theme of its policy in Latin America.
But the diplomatic equation has shifted.
Washington no longer is consumed by the view that the Sandinistas threaten the security of the hemisphere, nor by the idea that the region's problems must be resolved by the US alone. And Latin America, while more politically and diplomatically independent, nevertheless is eager to engage in a more cooperative relationship with the Colossus of the North.
The scene has changed in part due to the Nobel Prize-winning diplomacy of Costa Rican President Oscar Arias, host of Friday's summit meeting with 19 heads of state. Mr. Arias, and not a US president concerned about the spread of Soviet and Cuban influence, is expected to set the tone of this meeting, which also celebrates the 100th anniversary of Costa Rican democracy.
The official agenda centers on the ``six Ds'': debt, drugs, democracy, development, disarmament, and deforestation. But the unofficial agenda revolves around the improved relationship between the US and Latin America.
``Bush's presence is an excellent signal for Latin America,'' says Luis Guillermo Solis, an official in Costa Rica's foreign ministry. ``It shows that the US has surpassed the extremely narrow agendas of the past.''
President Reagan's Central America policy devoted itself mainly to helping overthrow the Sandinistas in Nicaragua and defeating leftist guerrillas in El Salvador.
Thus the former administration found itself at odds with several Latin American organizations and regional accords, even the 1987 Central American peace agreement fashioned by Arias.
``Under President Reagan, such groups ... were seen as working to thwart US policy,'' says Susan Kaufman Purcell, a Latin America expert at the Council on Foreign Relations in New York City. ``There was a feeling that going to these meetings would be unproductive and would only pit the US against the rest of Latin America.''
Few expect such tensions this week. A senior Bush administration official described the White House agenda as the ``celebration'' of invigorated democracy in Latin America.
Another official stressed that Bush ``is working hard to create a new partnership with Latin American leaders.''
That spirit is a far cry from the go-it-alone attitude of the past.
``The Bush administration is recognizing quietly that the unilateral policy of the Reagan administration failed,'' says Adolfo Aguilar Zinser, a Mexican academic who closely monitors US-Latin American relations.
During Reagan's tenure, ``the US always fell back on cold-war arguments in dealing with Latin America,'' Mr. Aguilar says. But with the thawing of East-West relations, he says, ``the US recognizes that security issues can't be cast in the same light.''
The US is still intent on discussing the contras' future and the upcoming presidential elections in Nicaragua. But the Bush administration now sees cocaine, not communism, as its greatest security threat in the region.
Even with a special ``drug summit'' expected next year between Colombia, Bolivia, Peru, and the US, the drug issue is expected to be near the top of the agenda during tomorrow's meeting in Costa Rica. Many Latin American countries now view drugs not just as a US problem but as a threat to their own security. And the US has shown a new willingness to cooperate with Latin countries.
The US likely will try to forge similar alliances with regard to Panama, whose leader was not invited. While a consensus exists among Latin nations that Gen. Manuel Antonio Noriega should leave power, most Latin leaders seem relieved that the US did not intervene in Panama earlier this month.
Arias will likely push for debt-for-nature swaps aimed at easing the debt burdens of developing countries while protecting their natural environments. In Costa Rica, four such deals have been struck so far, trading more than $68 million of debt to outside conservation groups or foreign governments.