Motorola’s relationship with mobile phone carrier Verizon has grown by leaps & bounds over the past few years. Motorola’s many acclaimed handsets, including the Motorola Droid, the Droid 2, and the Droid X, are available only through Verizon.

According to a filing with the Securities & Exchange Commission, sales of Motorola handsets through Verizon made 13 per cent of Motorola’s total revenue in 2008 and 17 per cent of total revenue in 2009.

In 2010, the figure jumped to account for 28 per cent of Motorola’s total revenue via Verizon. But, the availability of Apple's iPhone 4 on the airwaves of Verizon could derail Motorola's growing partnership with the carrier.

Motorola admitted that the launch of new and highly-efficient handsets through Verizon could result into a considerable reduction of revenue from Verizon.

In the document filed with the SEC, Motorola said, "If any significant customer, particularly Verizon or Sprint Nextel or other large customers, such as Comcast, stopped doing business with us, or significantly reduced the level of business they do with us, our financial results could be negatively impacted."

Motorola has already started finding out new carriers for its handsets. The Motorola Atrix 4G will be made available from January 22 via AT&T.