Poland's military and party leader, Gen. Wojciech Jaruzelski, thanked President Leonid Brezhnev today for his understanding of the "dramatic and difficult situation" in Poland and for Soviet economic aid.

"Polish society has been able to convince itself once again that at difficult moments it can always count on its Soviet friends," said Jaruzelski in a telegram saluting Brezhnev on his 75th birthday. It also was signed by Poland's head of state, Henryk Jablonski.

Brezhnev, amid an outpouring of public tributes, asserted that the entire Kremlin leadership was behind his policies: "a united opinion about the goals of our policy, domestic and foreign, and about the paths leading to these goals."

The Soviet leader made no reference to the situation in Poland. But his remark about Politburo unity seemed designed to reassure the public that there have been no top-level disagreements at a time of crisis.

The official Soviet news agency Tass renewed charges of U.S. interference in Poland and reaffirmed that Poland "will remain" a "firm link in the Warsaw Pact."

The congratulatory message from the Polish authorities pledged that the military council that took power last Sunday would remain faithful to the ideals of socialism.

Brezhnev, surrounded by his Kremlin colleagues and East European allies -- except for the absent Poles -- again received the Soviet Union's highest awards, the Order of Lenin and the gold star of a Hero of the Soviet Union. The leaders of Hungary, Bulgaria, Czechoslovakia, East Germany, Romania and Mongolia presented similar awards to him yesterday.

Well-informed sources said the leaders focused on joint economic assistance to Poland. The sources said the main issue was emergency food supplies, presumably to shore up the martial-law government and help it gain a measure of public support.

The summit conversations were described as informal, apparently to avoid the need for a formal communique.

Gen. Jaruzelski said Poland will apply "the universal principles of Marxism-Leninism to national Polish conditions."

A Tass dispatch from Warsaw today reported continuing return to normal despite "disorders" and rare attempts to stage strikes. It quoted Polish authorities as saying there were still "serious difficulties" in supply of raw materials and electricity but "the work rhythm in industry is picking up."

But the Soviet media were dominated by the Brezhnev birthday celebrations, with roughly 75 percent of space in all newspapers devoted to personal tributes, reviews of Brezhnev's book and exhibitions devoted to his political career.

A message from Soviet Georgia, published in the Communist Party newspaper Pravda, referred to him as the "recognized vozhd supreme leader of the Soviet people," a term normally used for Josef Stalin.

In a later speech today, Brezhnev again mentioned that the Kremlin leadership was united in its foreign policy but this time specified that he was talking about his policy of detente. He said he had been questioned by foreign leaders on whether "others in the Soviet Union" were committed to his policy.

"I should like to say to the gentlemen who reason along these lines: little do you know about the Soviet Union. Brezhnev's dedication to the cause of peace is to be explained by the fact that he speaks the thoughts and sentiments of the entire Soviet people and, of course, of the entire Soviet leadership and expresses the firm and undeviating policy line of our party and state."

Tass, in again accusing President Reagan of interference in Polish internal affairs, said that the United States would like the situation to develop to a point where it would resemble that in Northern Ireland.

Tass said Washington was "casting about for the ways to worsen the situation in Poland so that the new year should not be ushered in in Poland with the hope that the main difficulties are past." It said attempts to break Poland's ties with the Soviet Bloc are "doomed to failure."