India's national security adviser, J.N. Dixit, has died in New Delhi. The Indian official had played a leading role in the peace process between India and Pakistan.

68-year-old Jyotindra Nath Dixit died Monday after suffering a heart attack, according to the prime minister's office. The career diplomat was appointed the country's National Security Adviser after a Congress Party-led government took power in May last year.

In recent months, Mr. Dixit was at the center of many crucial discussions with Pakistan, with whom India has been engaged in a peace process since last January.

Independent foreign policy expert Brahma Chellaney says Mr. Dixit was playing a key role in talks not only with Pakistan, but also China, with which India fought a brief border war in 1962.

"Mr. Dixit was actually engaged in back-channel diplomacy with Pakistan, and he was also India's negotiator with China on the border issue," said Mr. Chellaney. "He also happens to be the key man in the nuclear command and control hierarchy."

Foreign policy experts say Mr. Dixit's death could temporarily slow the momentum of the dialogue with Pakistan, because he had developed a personal rapport with his counterparts.

In 1991, the high-profile diplomat was serving as foreign secretary when India's staunch ally, the Soviet Union, collapsed. The end of the Cold War saw him reach out to forge closer ties with the United States, among other countries, as New Delhi attempted to adjust to a changing world order.

Mr. Dixit also served as India's ambassador to several countries in the region, including Bangladesh, Afghanistan, Sri Lanka and Pakistan.