The incoming Bush administration, with Bush himself a keen foreign affairs activist who has named his closest confidant as secretary of state, is poised to pursue an extremely active foreign policy.

A key effort, according to senior U.S. officials, Bush advisers and other analysts, will be to accelerate the growing global trend away from the U.S.-Soviet military confrontation that has dominated the postwar world, toward a more fractious global economic competition.That trend, which already has brought powerful new participants like Japan to the international playing field, holds new perils for the United States. Growing demands for political and economic reform are causing havoc from eastern Europe to Latin America and the Far East.

Struggles between the United States and its allies over trade, currency regulation and finance are causing new frictions and severely straining the NATO alliance that is more used to dealing with manageable security issues.

"The greatest threat to U.S. security over the next few years," said former State Department official Robert D. Hormats, "may well come not from Moscow but from a confluence of economic difficulties that jeopardizes international political stability, disrupts U.S. alliances and undermines the capacity of the United States to pursue its global interests."

At the same time, aides say Bush and Baker intend to push harder on a theme they helped implant during the Reagan administration: that democratic reforms cause more openness, technological innovation and economic growth, leading perhaps more surely to international stability than an approach relying primarily on military power.

Indeed, recent U.S.-Soviet cooperation on arms control and regional conflict suggests the two superpowers recognize that, while strong defenses are necessary, neither can afford an arms race that is not tempered by arms control and other forms of cooperation - measures Bush said he will pursue aggressively.

"This is a time of watershed events and watershed rearrangements in thinking," Secretary of State George P. Shultz said recently with characteristic understatement.

Credit for recognizing these changes goes to Shultz and President Reagan, who hammered on the linkage of democracy and economic growth in a notable speech last spring at Moscow State University. But the job of grappling with the issues falls to the more pragmatic Bush and Baker.

The 56-year-old Baker, an affable, wily and sometimes ruthless Texan and former treasury secretary, is "just the guy" to cope with the challenge, Shultz happily declared last week.

The federal budget squeeze will afford Bush and Baker little leeway for bold new initiatives like a Marshall Plan for Central America; instead, Baker is expected to press Japan to turn over more of its capital surpluses to Third World aid to help ease severe crises in countries like El Salvador and the Sudan.

The new administration also will move assertively to temper the recent binge of European bank lending to the Soviet Union, urging a more cautious approach until it becomes evident that the Kremlin is putting the brakes on its military expansion.

Bush aides also expect a new diplomatic offensive early in the administration aimed at breaking the impasse over Nicaragua.

Although the idea hasn't yet been firmed up, aides said it could involve a conciliatory new U.S. offer of negotiations, coupled with the implied threat of renewed military aid to the Contras if Nicaragua's Sandinista government balks.

Such an initiative would rely heavily on Baker's ability for political salesmanship on Capitol Hill.

But congressional leaders last week indicated a willingness to work with Baker despite skepticism and outright disagreements over issues such as funding for "Star Wars" anti-missile defenses.

House Majority Leader Thomas Foley, D-Wash., said Baker "has wide respect in both parties on (Capitol) Hill." Even Sen. Christopher J. Dodd, D-Conn., who fought Reagan to a draw on Contra aid, had high praise for the secretary of state-designate.

Baker's popularity even among his opponents is a tribute to his political skills, said Donald Regan, treasury secretary and White House chief of staff under Reagan.

"He's the most astute politician we have," Regan said, adding that that skill will be useful in dealing with world leaders like Soviet leader Mikhail Gorbachev, who, Regan noted, is a consummate politician himself.

Unlike Shultz, Baker is not a trained economist. But he is widely credited with having helped create a framework for the Western Allies to deal cooperatively with finance and trade issues and with working with Japan to reduce trade frictions.