The appointment of former French Finance Minister Jacques Delors as president of the European Commission will have little impact on European Community-United States economic and trade relations.
But it could be the spark that ''relaunches'' Western Europe following a period of decline, diplomats here say.
Mr. Delors, who replaces Gaston Thorn of Luxembourg, is widely respected in Europe and abroad for his handling of the French economy since becoming finance minister nearly 31/2 years ago. His four-year term begins Jan. 1.
A moderate Socialist, Delors has pushed policies more akin to supply-side economics than to traditional socialist theory. His 1985 French budget, for example, calls for cuts in personal income taxes and in local taxes on companies as well as reductions in public spending.
But he has annoyed US officials with sharp criticism of US economic policy, which he says has harmed Western Europe. Some US officials consider him to be extremely narrow-minded on international financial and trade issues.
Last year Delors floated the idea of restricting exports of West European capital to the US as one way to stem the rise of the American dollar. And he has resisted US calls for regular joint meetings of Western trade and finance ministers to discuss interrelated problems.
Also annoying US (and some West European) officials has been the Delors-led French opposition to a US-sponsored plan to begin a new round of international negotiations under the auspices of the General Agreement on Tariffs and Trade aimed at liberalizing world trade.
What could affect EC-US relations more than the appointment of Delors, according to diplomats here, is the almost certain departure of External Relations Commissioner Wilhelm Haferkamp and Vice-President for Industrial Affairs Etienne Davignon from the 14-member commission at the end of the year.
Mr. Haferkamp has been a moderating voice in the often-bitter trade disputes that have marred the EC-US relationship in recent years.
Mr. Davignon, the second most powerful member of the commission, has displayed remarkable good humor even as he negotiated with extreme skill on various EC-US trade questions. It was he who masterminded and carried out on the EC side the deal signed with the US in October 1982 limiting EC steel exports to the US market.
''Davignon has probably done more than any other EEC official to keep US-EEC relations on an even keel,'' said a US diplomat here.
It is significant that the EC has picked a finance minister as the commission's new chief. Decisionmaking at the EC has been stalled for at least four years as the organization's financial crisis has worsened.
Just this week, Mr. Thorn warned that spending to support farm prices will have to be halted this fall unless EC governments quickly approve new funds for the EC budget.
Probably the toughest task facing Delors will be the need to cut EC farm spending, including export subsidies, which take up about two-thirds of the organization's roughly $20 billion annual budget. The US has criticized the Community's export-subsidies policy, claiming it has resulted in rising EC sales on world markets at the expense of the US.
Diplomats here expect Delors to come up with some fairly creative recommendations for getting the EC out of its budgetary mess and getting on with implementing practical projects that could be of real benefit to the Community, especially in the industrial field.