Winston Churchill II, grandson of the late British prime minister, visited the White House yesterday as part of a delegation of Western European figures urging Congress to release $14 million in aid to "contra" rebels fighting Nicaragua's Sandinista government.

The visit by the British member of Parliament and a dozen other persons was part of a White House effort to gain the backing of various groups to help push Congress on the aid issue. The group presented a petition to Congress declaring that aid to the rebels is "indispensable."

After a White House session at which President Reagan made a brief appearance, Churchill told reporters that the United States should attempt to halt the spread of communism in Central America now "when the stakes are relatively low."

If this effort fails, he said, "we may wake up five or 10 years from now to find that the allies of the Soviet Union are on the Rio Grande and you do, indeed, have to commit U.S. forces and that this could be a Vietnam-type involvement, which we are so desperately anxious that you should avoid."

Count Franz-Ludwig von Stauffenberg, a member of the European Parliament, whose father was a leader in the unsuccessful plot to assassinate Adolf Hitler on July 20, 1944, said, according to United Press International:

"This is not a question of whether this is a rightist or leftist regime in Central America states. The question is whether it's humanitarian, whether it's on the basis of human rights or not. We, as democrats, should fight for the implementation of human rights and democracy and should fight all efforts that are directed against" them.

Later, the delegation participated in a Capitol Hill seminar chaired by former U.N. ambassador Jeane J. Kirkpatrick and entitled, "How to Prevent Democracy from Perishing in Central America."

White House officials said the 13-member delegation was sponsored by Resistance International, a Paris-based human rights organization, and the American Foreign Policy Council, a privately financed Washington group that seeks to provide foreign affairs advice and information to Congress.

Other members of the delegation included former Australian prime minister J. Malcolm Fraser; Luc Beyer de Ryke, a member of the European Parliament; French writer Jean-Francois Revel; Kai-Uwe von Hassel, member of the German Bundestag; Marie Madeleine Fourcade, a well-known French World War II resistance leader; Monique Garnier-Lancon, vice president of the European Institute for Security, and Edgardo Sogno del Valino, Italian World War II resistance leader.

The Western European delegation was one of many groups lobbying on both sides of the aid issue, even as a compromise appeared to be unfolding yesterday.

After meeting with Reagan, the group received a briefing from National Security Council officials on the administration's view of the situation in Central America.

Albert Jolis of Resistance International said it was founded in 1983 by "a group of intellectuals, dissidents and defectors from communist countries," including those who are in Latin America.

Ron Nelson of the American Foreign Policy Council said his group was started three years ago to provide "educational information" to House and Senate members about foreign affairs. He said the delegation was organized to offer a "European view of the situation in Central America, in particular Nicaragua."

The petition, addressed to Congress, was published yesterday as an advertisement in The New York Times. It said the ruling Sandinista government has "not succeeded in breaking the resistance of the Nicaraguan people." The document also said the Sandinistas' political agenda "remains a totalitarian one."

In addition, the document warned that aid to the contras should be provided on a foreign policy basis and because it is "necessary morally."