HOUSTON, JULY 11 -- They are an international odd couple, the tall, slim Yankee with a penchant for caution, and the big, bluff German pushing his country toward unification. But President Bush and West German Chancellor Helmut Kohl seem to have formed a diplomatic partnership to try to manage Europe's headlong drive toward a new order.

Brought together by international events, their alliance is part marriage of convenience and part mutual admiration society, a personal relationship of candor and teasing humor.

Not that they agree on all issues. Here at the economic summit they have been on opposite sides of the three principal items on the agenda -- aid to the Soviet Union, international trade and the environment. But each has repeatedly gone out of his way to show public understanding of the other's problems, and passed up chances to voice their deep disagreements.

"Chancellor Kohl understands the difficulties of the United States" on the question of aid to the Soviet Union, West German spokesman Hans Klein said Tuesday. On his unsuccessful push for a joint Western aid program, Kohl shrugged off the dispute today, saying, "Each of us has had political discussions in our own country {on this question}. The United States has a very difficult economic situation, and there is the problem of Cuba."

On the environment, where Kohl similarly lost a push for quick cleanup of greenhouse gases, he noted with a smile, "We have various positions. I have to respect that the situation in the United States is different."

Bush was equally Mr. Nice Guy. "Well, Germany has some very special interest that we understand," he said today on the subject of aid to Moscow. "We're not urging everybody to march in lock-step."

People are starting to notice. Asked at his news conference today if he has "developed a special working relationship" with Kohl, Bush replied that the relationship is "hard to explain. I do think that the Germans appreciate the fact that we have stood at their side on this question of German reunification." He described Kohl as a "bulldog" and a "fighter."

A reporter asked whether Kohl had supplanted British Prime Minister Margaret Thatcher in U.S. affections? Not at all, said Bush. "You're going to get me in trouble; they haven't even left town here."

According to Klein, the two men "sort of have the same wave length. It's not only external conditions, it's also a congruence of minds." And, he added, "Both like a good joke."

Although they can speak only through interpreters, a bond began to form between them in 1983, when then-Vice President Bush's motorcade was stoned by anti-nuclear demonstrators during a visit to Krefeld, West Germany. Kohl angrily defended U.S. deployment of nuclear weapons in Germany, denounced the rioters and demanded an inquiry into the event by state authorities, for which Bush expressed gratitude, a German official said.

Last February, the two spent a weekend together at Camp David, the presidential retreat in Maryland, where aides to both said they spent more time than leaders usually do talking about their families, their love of politics and their enjoyment of the outdoors. "The Camp David visit was the genesis of a real personal relationship," an administration official said.

Since then, there have been numerous phone calls and several more meetings devoted to managing the unification issue and to Soviet President Mikhail Gorbachev's Washington summit with Bush.

Even in private meetings here, Kohl repeatedly expressed understanding of Bush's position, aides said, especially on Soviet aid. German officials said they were content to wait to push for concrete American action until after the U.S. elections in November, when they believe Bush may feel freer to help.

Although theirs is a diplomatic relationship, politics may be the key to understanding it. "Both of them are experienced politicians and know that in democracies, politicians and parties want to be reelected and there are things parties have to consider," Klein said. "And they talk openly about it."

At a time last winter when Kohl was equivocating in public about respecting the inviolability of the Polish border with Germany, he explained to Bush in private conversations the domestic political pressures he faced because of upcoming elections. "Once it was explained to Bush, he understood," a German official said.

Added an administration official, "His private commitment to Bush was that he'd respect the border."

In private, the two reportedly tease one another and often break up a serious discussion with humorous digs at each other. But aides to both men recognized that the relationship could not have developed as it has without the fall of the Berlin Wall eight months ago.

"Bush and Kohl were driven together by circumstances," an administration official said. "With the U.S. wanting to have a leadership role {in Europe} . . . Bush recognized that he needed to be close to Kohl."

In return, the German leader has gone out of his way to stroke the president and to consult regularly on developments in Europe. According to German officials, Kohl uses the word "glucksfall" to describe Bush. Translated literally it means "serendipity," but Klein defines it more loosely. It means, he said, "a case of luck for Germany."