India may temporarily shut down BlackBerry services if security concerns are not addressed in a meeting on Thursday, sources said, in a signal the Canadian firm's tussle with authorities around the world is far from over.

The latest ultimatum for BlackBerry maker Research In Motion comes a day after the company agreed to hand over user codes that would let Saudi authorities monitor its BlackBerry Messenger, as it seeks to stop the kingdom from silencing the service, a source said on Tuesday.

In a matter of a few weeks the BlackBerry device -- long the darling of the world's CEOs and politicians, including U.S. President Barack Obama -- has become the target for its encrypted email and messaging services.

India, like several countries in the Middle East and North Africa, want access to encrypted Blackberry communication, which has been linked to militant activity including the Mumbai attacks in 2008 that killed 166 people.

The government would meet with telecoms operators on Thursday, India's internal security chief U.K. Bansal told Reuters on Wednesday, but it was not clear if RIM would take part in the meeting.

RIM declined to comment.

India's home (interior) ministry will press on Thursday for some deadline to be fixed for RIM to share encryption details.

There definitely could be talk of some deadline and a proposal to take strong action on BlackBerry services during the meeting, said a government official, who declined to be identified as he is not authorized to speak to the media.

Another senior Indian government official told Reuters that mobile phone operators could be asked to shut down RIM's Enterprise Email and Messenger services temporarily as a last alternative, if RIM does not agree to offer access to data.

If they cannot provide a solution, we'll ask (mobile) operators to stop that specific service. The service can be resumed when they give us the solution, the source said.

The responsibility to meet Indian security requirements rests with mobile phone operators in India rather than RIM.

SAFE AND SECURE?

Much of BlackBerry's success over the past years has been its secure network, allowing executives to communicate safely, but one of its top selling points has now become a problem.

The German government has banned politicians and civil servants from using the BlackBerry and the European Union Commission this month rejected the BlackBerry in favor of Apple's iPhone and HTC smartphones.

RIM, unlike rivals Nokia and Apple, operates its own network through secure services located in Canada and other countries such as Britain.

RIM has said BlackBerry security is based on a system where the customers create their own key and the company neither has a master key nor any back door to allow it or any third party to gain access to crucial corporate data.

China and India are the world's largest mobile phone markets and any move to restrict usage could deny RIM significant revenue potential in coming years. There are more than 635 million mobile phone subscribers in India, second only to China.

Bharti Airtel and Vodafone's India unit are the largest providers of BlackBerry services in India, the world's fastest growing market and key for RIM.

The controversy comes at a difficult time for RIM as it battles growing consumer demand for smartphones running on Google's Android platform, particularly in the United States, and Apple's latest iphone 4.

The launch of RIM's new model BlackBerry Torch aimed at countering the growing competition was overshadowed by the firestorm over data encryption.

MILITANT THREAT

Authorities fear that the BlackBerry email and messaging services could be used by militants as security agencies cannot access the messages sent through these services.

India cracked down on the entire mobile phone market after Pakistani militants used mobile and satellite phones to coordinate Mumbai attacks. Authorities banned pre-paid phone subscriptions and still do not allow text messages in the volatile region of Kashmir.

While some governments are citing national security concerns, others are also citing social worries the encrypted messenger service enables, such as spreading pornography.

As of now there is nothing more to comment on this issue, a RIM India spokesman said on Wednesday, when asked if a breakthrough was in sight.

India's security establishment took a hardline view on RIM's stance that it does not possess a master key to intercept data traffic on BlackBerry, insisting it needs access to encrypted messages in a readable format.

If enforced, an estimated one million users in India would only be able to use these devices for calls, text messages and the Internet.

Indian officials say RIM has proposed to help India track emails, without sharing encryption details, which security officials say is not enough.

(Writing by Paul de Bendern; Editing by Lincoln Feast)

Blackberry India