INMARSAT, the international satellite communications company, will today announce that it is to be sold to Apax and Permira, the buyout firms, for about $1.5 billion (£900 million).

The decision marks a U-turn by Inmarsat, which last week said it would enter non-exclusive talks with Apollo Partners and Soros Private Equity, two US buyout firms, after failing to secure a deal with Apax and Permira following a week of exclusive negotiations.

The latest round of bids had Apollo and Soros offering $15.10 a share and Apax and Permira bidding $15 a share.

A source close to Apollo and Soros said the two firms had been confident of closing the sale within days of entering discussions with Inmarsat.

Both sides are understood to have spent millions of pounds on the year-long bidding war, and Apollo and Soros were understood to be shocked that they lost in spite of their higher offer. The source said last night: “We are currently reviewing our options.”

The Apax-Permira bid has led to calls for a White House inquiry into whether Inmarsat’s sale to the two UK-based equity firms might harm US security. One of Inmarsat’s biggest customers is the US Navy, which used its services during the recent Iraq war.

Several senators and congressmen have demanded that the Committee on Foreign Investments in the United States (CFIUS) open an investigation. The CFIUS panel makes recommendations when strategic assets are sold to foreign bidders. However, Inmarsat is thought to consider the investigation a minor hurdle.

The company, based in London, began as an intergovernmental organisation providing communications for shipping fleets, but was privatised in 1999 and now serves airlines, the media and the military.