SAN FRANCISCO (Reuters) - Apple Inc's new iPhone, already racking up blockbuster sales with consumers, appears to be making small but steady inroads into the coveted U.S. corporate market dominated by Research in Motion Ltd's BlackBerry.

While most companies are unwilling to abandon their trusted BlackBerries, analysts say a grassroots movement may be taking place among employees -- particularly at small and mid-size companies -- who have bought their own iPhone and are convincing their employers to support it.

"I see very few companies turning off BlackBerries," said Jack Gold, founder of research firm J.Gold Associates. "I see more companies turning on support for the iPhone."

Gold estimates at least 15 to 20 percent of people who buy the iPhone are going to use it for business reasons. "Those are people who have gone out and bought these things and have taken it to a company and said 'make it work,' or have made it work somehow," he said.

Apple sold 6.9 million units of its new 3G iPhone in the September quarter, versus 6.1 million BlackBerries. Although iPhone sales are widely expected to be hurt by the economic downturn, the gadget's fast start had the industry buzzing.

Apple fired its opening salvo in the battle for the enterprise market last March, when it announced that the 3G iPhone would feature Microsoft Corp's Exchange for corporate e-mail and other new security standards.

At the time, big names like Genentech Inc, Nike Inc and Walt Disney Co announced they would support the iPhone. Genentech said it would deploy 3,000 to employees.

Still, no one doubts that the BlackBerry continues to own the enterprise space. Apple will have a tough time cracking industries such as finance and government, which have higher email security requirements, analysts say.

And Apple may view the enterprise market as simply icing on the cake of its consumer success. The time, effort and money required to satisfy corporate customers may not be something Apple is interested in.

Of course, RIM is making its own push in the opposite direction. Its as-yet-unreleased touch-screen Storm smartphone is a play for the consumer market.