West German Chancellor Helmut Kohl hopes to obtain new assurances of U.S. flexibility in the Geneva arms control talks from President Reagan this week in order to carry a positive message to Soviet Leader Yuri Andropov when Kohl travels to Moscow on July 4, according to Chancellery and Foreign Ministry officials here.

Kohl's trip to Moscow is considered here the most crucial diplomatic effort this year to nail down an arms control agreement, and he is anxious for assurances of cooperation from Washington during his trip to the United States for the Williamsburg economic summit.

Senior government officials in Bonn are concerned by what they perceive as a growing conviction in the Reagan administration that Pershing II missiles must be deployed in West Germany later this year before the Soviets will bend toward a plausible compromise.

While prepared to deploy the missiles if necessary, the Kohl government wants to explore every possible avenue to curtail medium-range nuclear weapons before the December stationing deadline.

Senior government officials in Bonn said they are pleased that chief U.S. negotiator Paul Nitze has gained more flexibility to explore possible compromises at Geneva. But they also said that they would like to see Nitze acquire even more authority and possibly revive the tentative proposal he reached last summer with his Soviet counterpart, Yuli Kvitsinsky.

During a walk in the woods near Geneva, Nitze and Kvitsinsky focused on an outline that would limit the Soviet Union to 75 SS20s and the West to 75 cruise missiles. The proposal was later rejected in Moscow and Washington.

A senior minister in Bonn said, "The walk in the woods deal was certainly something we could live with."

When he meets privately with Reagan, Kohl hopes to extract a conciliatory message he can take to Moscow in early July. This might include another plea for lower missile deployments or new overtures for an East-West summit, something that Kohl has advocated since taking office last October.

Despite his conservative leanings, Kohl acknowledges the need to shore up West Germany's ties with the East Bloc and is particularly eager to enhance western dialogue with Moscow.

From the Soviet viewpoint, Bonn has emerged as the most likely interlocutor in the prospective bid to repair East-West relations. Moscow's traditional diplomatic conduit to the West, through Paris, has been stymied by poor relations with the Socialist-led government of Francois Mitterrand.

The summit participants are expected to reaffirm the West's steadfast intention to deploy 572 cruise and Pershing missiles in Europe later this year unless the United States and the Soviet Union reach an accord at the Geneva arms control talks.

West German officials are relieved by the Reagan administration's decision to consign the controversial issue of East-West trade to a minor place on the summit agenda.

But they said a new row possibly could erupt over protectionism, pitting Japan against the Europeans and Americans, who have long argued that Tokyo must lower barriers to foreign imports.

European countries have grown more optimistic about the strength of the U.S. economic recovery. Nonetheless, there are lingering worries about the massive U.S. budget deficit and the related danger that interest rates could rise again and thus abort an economic upturn, Bonn officials said.

Another issue that could raise problems is how to stabilize key currencies. There is little enthusiasm in Bonn, London or Washington for Mitterrand's call for "a new Bretton Woods" that would resurrect fixed exchange rates.

West German officials said last week's Paris-Bonn summit between Kohl and Mitterrand resulted in "the most frank discussions we've ever had."

Bonn fears that the Socialist government in Paris will not be able to resist widespread domestic opposition to austerity measures. If Mitterrand should offer concessions, the West Germans are worried that they will be forced to spend heavily to rescue the franc again this autumn.

The problems of the international economy have grown so complex that few analysts expect more than anodyne vows of good will to emerge from the Williamsburg session.

West German officials say a final "common declaration" will include strictures against the dangers of protectionism and high interest rates. It will also express support for developing countries and encouraging words for the United Nations Conference on Trade and Development, which will meet a week later in Yugoslavia.

"We already have enough difficulties," explained a Chancellery aide. "Our main goal is not to create new problems. We know we simply cannot achieve more than cautious promises."

Besides economic matters, the seven western leaders also plan to discuss such political topics as disarmament, East-West relations and the Middle East.

While the sensitive issue of trade with the East Bloc has declined in importance, Bonn sees some merit in exploring how the West could revive a dialogue with the martial law regime in Poland. Kohl is known to believe that if Pope John Paul II's trip there goes well next month, the West should take steps to dissolve sanctions against Warsaw.

On the Middle East, the summit leaders are expected to endorse the Israeli-Lebanese accord calling for withdrawal of all foreign forces, which recently was negotiated by Secretary of State George P. Shultz. The Europeans, in particular, will be urged to exert their influence to elicit Syria's cooperation with the troop withdrawal pact.