KARACHI, Pakistan, April 12 — The Pakistani Government announced today that it had received a note from Premier Chou En‐lai of Communist China strongly supporting its efforts to put down a movement for autonomy in East Pakistan.

The Government said that Premier Chou had denounced the United States, the Soviet Union and India for “carrying out gross interference in the internal affairs of Pakistan” and had promised China's support “should the Indian expansionists dare to launch aggression against Pakistan.”

[United States officials said that they did not believe that the Chinese message presaged any direct involvement by Peking in the Pakistani situation. In Moscow, Premier Aleksei N. Kosygin met with the Pakistani and Indian Ambassadors.]

A Letter to Yahya

In reporting Mr. Chou's statements, the Pakistani Government's news agency said that they had come in a letter to President Agha Mohammad Yahya Khan.

The message was welcomed here as China's firmest and most specific declaration of support for Pakistan since the military crackdown in East Pakistan began on ‘March 25. No formal comment on the message was immediately forthcoming from the Pakistani Government, but news of it was broadcast by the Pakistani radio.

As quoted by the news agency, the letter ended: “Your Excellency may rest assured that should the Indian expansionists dare to launch aggression against Pakistan, the Chinese Government and people will as always firmly support the Pakistani Government and people in their just stuggle to safeguard their state sovereignty and national independence.

No details about the eventual support were given.

“Of late,” Premier Chou was quoted as having said “the Indian Government has been carrying out gross interference in the internal affairs of Pakistan by exploiting the internal problems of your country. And the Soviet Union and the United States are doing the same, one after another.”

Since the fighting broke out. In the East, Pakistan has made repeated allegations — denied by India—that Indian armed infiltrators had entered East Pakistan to aid the independence forces of Sheik Mujibur Rahman, head of the Awami League, the major party in the East.

In his letter, the Chinese Premier praised President Yahya, saying “Your Excellency and the leaders of various quarters in Pakistan have done la lot of useful work to to uphold the unification of Pakistan and to prevent it from (moving toward a split.”

“In our opinion” the letter continued, “the unification of Pakistan and the unity of the people of East and West Pakistan are basic guarantees for Pakistan to attain prosperity and strength. The Chinese Government holds that what is happening in Pakistan at present as purely an internal affair of Pakistan which can only be settled by the Pakistani people and which brooks no foreign interference whatever.”