Western European heads of government today threw their support behind a multibillion-dollar rescue package for Poland that is a critical element in the Eastern European nation's struggle to work itself out of its poltical and economic crisis.

The Western leaders coupled their expression of support for the Poles with a warning to the Soviet Union not to intervene there, a sentiment underscored by British Prime Minister Margaret Thatcher, who said at the end of a two-day European Community economic summit meeting here:

"I think we must make it possible for Poland to solve its own problems its own way." In relation to the current heightened tensions in Poland, she added, "We have been continually concerned. Obviously we are watching everything closely, anxiously."

The statement by Western Europe's poltical leaders is s critical signal to major banks who are part of the $10.9 billion package sought by the Poles. Following the initial Polish request earlier this month, skeptical international bankers said that the attitude taken by the governments involved would be central to thier own decisions.

British Foreign Secretary Lord Carrington said the Poles also need more than $1 billion in short-term credits by July, when talks on the overall package are expected to be concluded.

[A State Department official said in Washington that the United States "is joining with other European countries in interim assistance for Poland . . . and is consulting with other Western creditors on long-term relief." The United States already has announced deferral of more than $80 million in credit repayments from Poland as an interim relief measure.]

The 10 heads of government gathered here clearly indicated that their decision went beyond economic considerations, linking the resolution of Poland's problems to overall European stability.

"The council notes that Poland has shown that she is capable of facing her internal problems herself in a spirit of reason and responsibility," the 10 leaders said in a joint declaration. "It is in the interest of the Polish people that Poland should continue to do so in a peaceful manner and without outside interference. It is also in the interest of stability in Europe."

Then, in a warning directed at the Soviet Union, which is now carrying out military maneuvers in Poland along with other Warsaw Pact troops, the declaration said, "The council is following recent development in Poland with great concern. It underlines the obligation of all states signatory to the Helsinki final act to base their relations with Poland on the strict application of the Carter of the United Nations and the principles of the final act" -- documents that are intended to protect the sovereignty of nations.

The $10.9 billion package would be made up of $3.4 billion in the form of new export credits guaranteed by Western governments, $4.4 billion in official Western debt, which Poland wants rescheduled, and $3.1 billion in debts to major banks, which Warsaw also hopes to refinance.

The European leaders did not go beyond a general statement of willingness to provide aid, leaving the details to be worked out by a consortium of Western nations in Paris and by representatives of the European Commission and European Council of Foreign Minsters.

Poland's outstanding hard-currency debt, now placed at more than $24 billion, has climbed steadily in recent months as the Warsaw government has been forced to continue to borrow heavily to cover the costly effects of work stoppages and slowdowns. Because of the large number of Western lenders involved -- including 15 governments and about 70 banks -- the Polish credit talks are especially complicated.

Without additional help from the West, Poland has said it would have to reduce imports from Western countries, most of which are bought on credit -- a move that certainly would aggravate already severe shortages in the troubled East Bloc country.

West German Foreign Minister Hans-Dietrich Genscher, who visited Warsaw last week, carried the recent request for Polish help to the summit meeting. Afterward, West German Chancellor Helmut Schmidt and French President Valery Giscard d'Estaing both noted in press conferences the substantial efforts already made by their own countries in extending credits to Warsaw and suggested it was up to other Western countries to follow suit.

The discussion on Poland represented the only foreign policy issue that drew the attention of European leaders at this summit conference away from a number of divisive internal European concerns, including squabbling over a common fish policy, wrangling over steel industry subsidies and a gloomy prognosis for their own economies.