Research In Motion’s BlackBerry laid claim to 10% of U.S. cell phone sales in Q2, according to Strategy Analytics.

The research firm said the BlackBerry was able to reach this milestone in a rough economic quarter when total mobile phone shipments rose 5.3% to 41.9 million units in Q2 2008 from 39.8 million in the year-ago quarter.

Although the Canadian BlackBerry maker represents no immediate threat to No. 1 device maker Nokia, which holds more than 40% market share, it is inching its way up the market share ladder.

Device maker Motorola clung to its No. 3 spot with 25% market share in Q2 by fighting off LG Electronics.