Prime Minister Narendra Modi of India announced on Wednesday that India had test-fired an interceptor rocket that shot down a satellite, escalating the country’s rivalry with China and Pakistan, and demonstrating a strategic strength that few countries can claim.

If confirmed, a successful anti-satellite test could destabilize the balance of power between India and Pakistan, both nuclear powers that for years have eyed each other warily, with hostilities briefly breaking out last month.

This technological leap puts India in the exclusive club of nations, along with the United States, Russia and China, that have proved their ability to destroy targets in space. This could be a crucial advantage in war, allowing a country essentially to blind another by taking out the enemy’s space-based communication and surveillance satellites.

It is no easy feat. In this case, scientists estimate that the satellite that India claims to have blasted apart was moving around the Earth at 17,000 miles per hour.

Mr. Modi made the announcement to a rapt nation just weeks before the country heads into a hotly contested election.