India has reaffirmed its commitment to 'no first use' of nuclear weapons but future policy will depend on the situation, the defence minister Rajnath Singh said.
Analysts said his comments introduced a level of ambiguity in a core national security doctrine.
India declared itself a nuclear weapons power after conducting underground tests in 1998 and long-time rival Pakistan responded with its own tests shortly afterwards. Since then, nuclear experts say the rivals have been developing nuclear weapons and the missiles to deliver them.
In a visit to Pokhran in western India, the site of the 1998 tests, Rajnath paid tribute to former Prime Minister and former leader of the ruling Bharatiya Janata Party, Atal Behari Vajpayee, for making India into a nuclear power.
"As far as our nuclear policy is concerned, our policy has always been 'no first use'. However, what happens in the future, depends on the circumstances," Rajnath said.
At the time of the 1998 tests, India said it needed a deterrent against nuclear-armed China but it has also long been concerned about Pakistan's nuclear capabilities.
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Tensions between the two nuclear-armed nations have increased following India's move to revoke autonomy in the disputed region of Kashmir, the cause of two of their three wars. In February, Indian and Pakistani fighter jets clashed over the territory.