Brussels — Although Europe has responded with unusual speed and solidarity in support of Britain in its dispute with Argentina, there is considerable uncertainty about how far this cooperation will stretch.
The British government, forced momentarily at least to accept American neutrality in return for US good offices as a mediator in the quarrel, has turned to Europe for diplomatic and economic support.
In a rapidly arranged working-lunch meeting here April 20, European Community foreign ministers reaffirmed solidarity with the British position and with the diplomatic efforts of US Secretary of State Alexander M. Haig Jr.
It seemed clear, however, that its allies refused to be drawn into backing the possible use of military force, which British officials were saying they could not rule out.
British and European sources here presented divergent interpretations of the support extended to the British use of arms to wrest back the Falklands.
A British source emphasized that Foreign Secretary Francis Pym had requested the meeting with his European Community (EC) colleagues as a special gesture of gratitude for the quick adoption of an arms and import embargo against Argentina last week.
But he made clear that other countries should understand that Britain felt the United Nations Charter granted states whose territory had been violated the right to military self-defense. Although he said London would exhaust all possible diplomatic means, the source added, ''We will not shrink from the use of force.'' He added, ''We are not in any doubt about our partners' backing'' on the question.
However, Belgian Foreign Minister Leo Tindemans, who chaired the EC ministerial session, later refused to be associated with any such interpretation. He repeatedly said the ministers did not discuss the military aspects of the situation, which he termed ''too uncertain and dangerous.''
Should Britain maintain its traditional isolated stand on the EC budget and farm policy, some EC countries might regard their recent display of support for Britain on the Falklands in a different light.
In addition to Britain, Germany, Italy, and the Netherlands have substantial trade and investment interests in Argentina. And possible economic retaliation against Europe by the Organization of American States or any of its members could put pressure on Europe. There have been reports Venezuela could block oil shipments to Europe in reply.
The acid test will come if Britain feels compelled to use military force.