Research In Motion (RIM) has assured Indian authorities of limited access to its Messenger services by September 1 and will hold talks this week on giving access to enterprise mail, a government source said on Monday.

RIM faces an August 31 deadline to give Indian authorities the means to read e-mail and instant messages sent over the BlackBerry.

They have assured partial access to its messenger services by September 1 and agreed to provide full access by the end of the year, a senior government source, who asked not to be named, told Reuters.

New Delhi says it will pull the plug if RIM does not comply, threatening its future in the world's fastest-growing telecoms market.

We hope they will address our security concerns, an interior ministry official said.

India is the latest country to step up pressure on RIM, which has built the BlackBerry's reputation around confidentiality.

Many business professionals and politicians prefer the device, but some governments, including Saudi Arabia, fear it could become a tool for terrorists or those breaking Islamic laws.

RIM has said BlackBerry's security is based on a system where customers create their own key, and the company has neither a master key or any back door to allow RIM or any third party to gain access to crucial corporate data.

RIM officials are expected to hold talks with the Indian government to explain the complexities of the enterprise mail system and try to find a solution, the government source said.

India's demands follow a deal with Saudi Arabia, where a source said RIM had agreed to give authorities codes for BlackBerry Messenger users. The United Arab Emirates, Lebanon and Algeria are also seeking access.

India, like other countries, has been criticized for seeking blanket restrictions, while mobile phone operators say they must offer consumers privacy and secure communications.

(Editing by Rina Chandran and David Holmes)