Research in Motion, maker of the BlackBerry, is headed for a showdown with the Indian government, which has revived a threat to shut off service in the country in a row over access to customers' emails.

India has toughened its position in the wake of reports that RIM has agreed to give the government of Saudi Arabia access to some of the codes with which BlackBerry customer data is encrypted when it passes across the Canadian firm's server network.

A string of emerging markets governments have been demanding RIM provide additional co-operation with their police and security services to allow monitoring of email and instant message traffic, in the name of national security.

Saudi Arabia threatened to block BlackBerry users' access to the smartphone's instant messaging service unless it won concessions from RIM, but it twice extended the deadline as negotiations closed in on a deal. An original plan for BlackBerry to locate servers in the kingdom appeared yesterday to have been superseded by an agreement to hand over some encryption codes.

That apparent success of Saudi Arabia's strong-arm negotiating stance emboldened the Indian government to revive its own threat to block BlackBerry services, which it originally made several weeks ago, only to withdraw it a day later.

India's home ministry has summoned the country's telecoms operators to a meeting today to discuss access to their BlackBerry users' data, and is expected to demand a deadline for RIM to share encryption details, with the threat of a suspension of some services if the deadline is not met. A senior government official told Reuters that the operators could be told to shut down RIM's corporate email and messenger services temporarily as a last resort. "If they cannot provide a solution, we'll ask operators to stop that specific service," the source said. "The service can be resumed when they give us the solution."

The BlackBerry instant messaging service has become popular across the Middle East as a means of communication between the sexes, where socialising in person would be frowned upon. In India, the government's concerns are driven not by social conservatism but by national security interests.

RIM has declined detailed public comment on any of the discussions it is having with governments, and said only that it is committed to treating governments equally and complying with local laws. It suggests that its encryption techniques are such that even it does not have all the codes needed for monitoring.

The issue has presented a tricky problem for RIM, which built its reputation on the security of BlackBerry communications, making the product particularly attractive to corporate and government users. When Barack Obama became the first US President to own a personal phone, it was a BlackBerry that was chosen. Now, however, BlackBerry has been seeking to expand sales in emerging markets, where anecdotal evidence suggests the recent series of confrontations and concessions has started to hit sales. Saudi phone sellers reported having to slash the price of the device after reports of RIM's climbdown began to emerge at the weekend.

A frustrated Michael Lazaridis, founder and co-chief executive of RIM, has argued that the governments' issue wasn't just about the BlackBerry, but about the modern internet. "Everything on the internet is encrypted," he said. "If they can't deal with the internet, they should shut it off."