President Reagan and West German Chancellor Helmut Kohl agreed yesterday to devise a comprehensive Western arms-control strategy to confront the Soviet Union with "realism, strength and alliance unity."

Kohl ended a two-day trip to Washington with a meeting and lunch at the White House in which he and Reagan congratulated each other on the recently signed Intermediate-Range Nuclear Forces Treaty and hailed a NATO effort to sort out potentially conflicting arms-control goals.

"We agreed that we must deal with the Soviet Union from a position of realism, strength and alliance unity," Reagan said in an East Room farewell to the chancellor.

A NATO summit meeting in Brussels March 2-3 "will provide an opportunity to continue discussions on these important matters within the alliance as a whole," Reagan said.

Since reaching agreement with the Soviets in December to eliminate land-based nuclear missiles with ranges between 300 and 3,125 miles, the United States and its allies have been discussing priorities for further talks with the Soviets.

Each of the 16 allies, depending on its politics and geography, has different interests to advance. The questions include how to deal with chemical weapons, how to reduce the perceived Soviet advantage in conventional forces and what to do about short-range nuclear weapons -- those with ranges below 300 miles.

Among the allies, West Germany has been most concerned about future military arrangements because of its position on NATO's front lines, and those concerns were reflected in Kohl's comments as he stood at Reagan's side.

"We were in agreement that all these disarmament questions and issues as well as the necessary measures to preserve our common security should be combined in form and overall concept for our alliance," Kohl said.

Touching on an area of disagreement between Bonn and Washington, Kohl repeated his view that East-West talks to reduce conventional weapons should include negotiations on tactical nuclear weapons.

A senior U.S. official who attended the meeting and talked about it to reporters on condition of anonymity said the United States continues to favor separate treatment of the two issues.

At the same time, the official said, the United States endorsed the idea of a comprehensive review of NATO arms control strategy.

The alliance agreed last year that its priorities should be to obtain an agreement to reduce long-range nuclear weapons first and then move toward reductions in chemical and conventional arms.

During Kohl's visit, the two sides have sought to minimize the importance of a controversy over new short-range nuclear weapons that the alliance will deploy by the mid-1990s. Some West Germans fear the weapons will invite Soviet attack, but Kohl said he does not favor their elimination.

His objective, he said, is "no denuclearized zone, least of all in Europe."

Reagan thanked the chancellor for Kohl's effort to lobby Capitol Hill for Senate ratification of the INF Treaty without reservations or amendments.

The treaty, Kohl said, "has for the first time in history opened the way toward genuine disarmament."

"The INF agreement is in the interest of the United States of America and in the interest of the Atlantic alliance and not least in the interest of our own country," Kohl said.

He added, "When I had talks with the leadership of the Senate, I pleaded in no uncertain terms for ratification of this agreement without restrictive amendments."