NEW DELHI, Aug. 9—India and the Soviet Union today signed a 20 ‐ year friendship treaty clearly intended to deter Pakistan from an attack on India.

Official Indian sources said, “We will be assured of essential supplies in case Pakistan should be stupid enough to launch an aggression.”

“Any country considering an attack on India will think twice before doing so,” the sources said.

The treaty, for which the groundwork had apparently been prepared secretly over the last several days, caught foreign diplomats here by surprise. It was signed at the Foreign Ministry this morning by the Indian Foreign Minister, Swaran Singh, and Andrei A. Gromyko, the Soviet Foreign Minister. Mr. Gromyko arrived in New Delhi only last night for a suddenly announced visit that seemed to have been arranged at India's request.

Relations between India and Pakistan have been deteriorating rapidly over the situation in East Pakistan, and each has issued warnings that she is ready to fight if the other at tacks.

Since March, the Pakistani Army, composed of West Pakistani troops, has been trying to crush the Bengali separatist movement in East Pakistan. The army repression has sent more than seven million Bengali refugees fleeing into India. For her part, India, which has already fought two wars with Pakistan, has been helping the Bengali guerrillas by providing sanctuary, training and arms.

Frequent, brief skirmishes between Indian and Pakistani troops have occurred on the border of East Pakistan.

New Delhi officials have ex pressed concern that Pakistan may attack India to divert attention from her military repression in East Pakistan.

The Indian‐Soviet treaty is not in a literal sense a military pact—its wording on what each nation must do in the event of an attack on the other is too flexible to qualify as such. But Indian officials were interpreting it as an assurance of military assistance in the event of a Pakistani attack.

Foreign Minister Singh, in announcing the treaty this morning in Parliament, said: “This should act as a deterrent to any powers that may have aggressive designs on our territorial integrity and sovereignty.”

Treaty Has 12 Articles

Much of the 12‐article treaty covers obvious ground, putting India and the Soviet Union in agreement on matters that they would already seem to agree on, in their increasingly close relationship. It commits the two nations, for example, to noninterference in each other's internal affairs, to nonaggression against each other, to efforts “to strengthen peace in Asia and throughout the world” and to an expansion of Indian Soviet contacts and cooperation in all fields.

The key clause, however, is Article 9, which says: “Each high contracting party under takes to abstain from providing any assistance to any third party that engages in armed conflict with the other party. In the event of either party's being subjected to an attack or a threat thereof, the high contracting parties shall immediately enter into mutual consultations in order to remove such threat and to take appropriate effective measure to insure peace and the security of their countries.”

This is not the language of a traditional mutual‐defense pact, but because of the treaty's apt timing and its likely psycho logical impact on an Indian pub lic aroused against Pakistan, it will nonetheless probably have the same favorable effect here.

Indian officials were buoy ant over the treaty; they had begun to feel angry and isolated by the policy of the other great powers — the United States and Communist China — in which some officials have even seen an anti‐Indian conspiracy. China is supporting Pakistan outright, and the United States is pursuing an ambiguous policy—giving sizable relief aid for the Bengali refugees in India, but at the same time continuing shipments of arms to Pakistan.

Prime Minister Indira Gandhi displayed her ebullience over the treaty before hundreds of thousands of people gathered here for a one‐day rally organized by the governing Congress party to demonstrate solidarity for the independence movement in East Pakistan and support for her policy.

Alluding to Pakistan's President, Agha Mohammad Yahya Khan, and his threats of imminent war with India, Mrs. Gandhi told the cheering throng, in Hindi: “Empty vessels make loud noise.”

The Prime Minister said the treaty was in no way a reversal of India's policy of nonalignment. “We must understand that if we are strong, tens of countries will come to our assistance. If we are weak, none will help us,” she said.

Soviet‐Indian collaboration has increased greatly in the last 15 years, particularly since the 1965 Indian‐Pakistani war, when Washington placed an embargo on arms to both combatants, but Moscow continued to supply arms to India. The Russians are now the largest supplier of military equipment to India.

Indian official sources said that they had “no need or de sire for foreign troops in our country and no desire to give military bases to foreign powers.”

The 20‐year accord will come into farce as soon as it is ratified by the legislative bodies in both countries, which the treaty says must take place within one month.

Mr. Gromyko, who met with the Prime Minister for an hour after the signing ceremony with Mr. Singh, will meet again with both officials tomorrow — although it is not clear what else they have to discuss.

Further talks, ceremonies and a dinner will be held on Wednesday, and a joint communique will be issued that evening. Mr. Gromyko flies back to Moscow Thursday morning.