Indian and Pakistani diplomats are exploring the possibility of a meeting next month between the leaders of the neighboring nations that once were united under the British but have fought three wars since independence as separate states 32 years ago.

Diplomatic sources here and in the Pakistani capital of Islamabad reported that messages between India's Prime Minister Indira Gandhi, sworn in just last week, and Pakistani President Mohammed Zia ul-Haq have suggested the summit meeting.

It would give Pakistan a chance to persuade India that any new arms it gets from the United States or China will be aimed toward Afghanistan, where the Soviet Union has massed an estimated 85,000 troops, not toward India.

Indian diplomats are not ready to accept those assurances but they would like the chance to dissuade Pakistan from rearming.

"Pakistan and India together could really make the Russians think twice about moving any farther," said a highly placed Indian diplomat.

Although India has had close relations with the Soviet Union, a long-range aim of its foreign policy has been to keep the superpowers out of the south Asian region -- where Indians consider themselves the dominant power.

While India is far stronger militarily than Pakistan, what one Western diplomat here described as "mutual paranoia" leads Indians to fear any move by another power to arm Pakistan. India is particularly worried about the formation of a United States-China-Pakistan axis arrayed against the Soviets in Afghanistan.

But diplomats here have noted that Indian officials have been restrained in their "highly predictable negative reaction" against the possibility of U.S. arms sales to Pakistan.

"No politician in India can publicly acknowledge that getting arms to Pakistan is good or acceptable," said a diplomat. "But after the first negative response, the reaction has been restrained. The Indians know the amount the U.S. is talking about supplying Pakistan cannot purchase a great deal of arms in anybody's market."

India has talked in recent years of its desire for a stronger Pakistan but that does not mean militarily strong.

Indians would like Pakistan to be a mini-India, with democratic institutions, some degree of economic growth, a way to transfer power without coups and an easing of regional and communal problems that threaten to split the country, a diplomat said.

"Pakistan hasn't made the same progress in that direction that India has. Pakistan is a military dictatorship, with vast regional differences, and that is worrying India," he added.

Gandhi confirmed those fears when she said in a preelection interview that she is most frightened of a weak neighbor and suggested that any arms Pakistan receives are likely to be used against its own people.

India is also concerned about the growing religious zeal in Islamic Pakistan, which it fears could spread to India. Although Moslems are only 11 percent of India's 650 million population, they are enough to make India the third largest Moslem country after Indonesia and Bangladesh. Pakistan, with a population of 80 million, is said to be 88 percent Moslem.

India would like to drive a wedge between Pakistan and such Moslem friends as Iran and Saudi Arabia, reminding Pakistanis that their cultural roots lie in south Asia, not the Arabian peninsula.

India would also like to stop the growing friendship between Pakistan and China, which is seen as a threat. China invaded India in 1962, an attack that helped solidify the Indian-Soviet friendship.

"We want to have a dialogue with the Chinese," said an Indian diplomat, "but anything we do with them is seen as provocative by Moscow."

The Chinese, meanwhile, have supplied many of the newer weapons for the Pakistani armed forces and have promised more. But, according to diplomatic sources in Islamabad, the Chinese notified Pakistan within the past three weeks that they no longer can give arms but must sell them.

Moreover, the Chinese currently are engaged in a major project to upgrade their own military and are able to supply only token amounts of the high-technology armaments the Pakistanis seek.

Chinese Foreign Minister Huang Hua has been in Pakistan since Friday.The official talks ended today in Islamabad, although Hua is not to return to Peking until Wednesday.

The United States has offered to supply Pakistan with $200 million worth of arms over the next two years in the belief that the greatest danger it faces in Soviet intimidation rather than direct invasion.

But even that amount of arms -- which could barely deliver 150 tanks at today's inflated prices -- is seen as provocative by India.

"If Pakistan goes in for major rearming," said an Indian diplomat, "India will do the same, which will be hard on us."

It will also be hard for the United States, which sees improved India-Pakistan relations as a cornerstone to Asian stability. In an effort to prevent a south Asian arms race, President Carter is sending Washington lawyer Clark Clifford here Jan. 31 with a personal message for Gandhi.

In this part of the world, personal contacts are important, which is one reason why a Zia-Gandhi meeting might ease some of the mutual distrust between the neighboring nations.