fter more than two years of negotiations, the United States and West Germany signed an agreement here yesterday intended to improve the speed and overall effectiveness with which American military reinforcements can reach Europe in time of crisis or war.

Signing for the United States, Ambassador Arthur Burns described the agreement, which includes a West German commitment to provide more military and civilian support for the six extra U.S. divisions that would arrive during a military emergency, as representing "important progress toward an enhanced and more rational division of labor within the Atlantic Alliance."

The agreement shows that the two countries, despite a certain amount of political distrust currently, can make common ground in the security area, Washington Post correspondent Bradley Graham reported. But yesterday's agreement on Wartime Host National Support is only the first item on a list of support measures that the United States is seeking from West Germany.

Discussions on other points, which call for Bonn to underwrite some of the major costs of modernizing and repositioning facilities used by the four U.S. Army divisions permanently stationed in West Germany, are continuing.

Bonn, pleading fiscal strain and other considerations, has been reluctant to assume new costs for America's peacetime military presence here. But the government found it could justify new outlays for wartime support.

Under the terms of the agreement, West Germany promises to provide 93,000 reservists to perform backup tasks for arriving American forces. The advantage of this is that, freed of some emergency airlift requirements, the United States can make more combat troops available.