Research In Motion, the BlackBerry's Canadian maker, gave no immediate indication that it would accede to the latest pressure from an emerging economy to open up its services to security agencies.
"If a technical solution is not provided by August 31, 2010, the government will review the position and take steps to block" BlackBerry email and messenger services, India's home ministry said Thursday.
New Delhi, battling insurgencies ranging from Kashmir in the northwest to the far-flung northeast, fears that heavily encrypted BlackBerry communications could be used by militants.
Islamic extremists used mobile and satellite phones to coordinate the 2008 Mumbai attacks that killed 166 people.
The Indian announcement came after Saudi Arabia on Tuesday postponed imposing a BlackBerry ban as the ultra-conservative Muslim country reported progress in solving its own security concerns.
The United Arab Emirates, however, has said it will ban BlackBerry messenger, email and web brows