– BlackBerry’s new Z10 smartphone goes on sale in the United States this weekend, almost two months after its debut in other countries, putting the company’s comeback plan to the test in its largest single market.

Chief Executive Thorsten Heins was scheduled to kick off U.S. sales of the device on Thursday night at a theater in New York’s Times Square. The event, with rapper Luda­cris and R&B singer Janelle Monae on the bill, marks the arrival of the Z10 at AT&T stores on Friday. The phone will be offered by Verizon Wireless next Thurs­day.

Heins is trying to reverse BlackBerry’s fortunes in the United States, where the one-time smartphone leader has lost ground to Apple’s iPhone and Google’s Android. Sales in the country fell by almost half to $520 million in the third quarter from a year earlier, through the U.S. still accounts for about a fifth of revenue for Waterloo, Ontario-based BlackBerry.

“There’s no risk of overstating the importance of the U.S. for BlackBerry,” said Ramon Llamas, an analyst with IDC in Framingham, Mass. “It’s such an important bellwether market.”

AT&T, the second-largest U.S. carrier, will offer the Z10 for $199.99 on a two-year contract, putting it at the same price level as the main iPhone. The phone was first unveiled Jan. 30, and it’s been available for weeks in Britain, Canada and other markets. Heins has attributed the U.S. delay to the longer equipment-testing procedures of American carriers.

Verizon Wireless, the nation’s biggest carrier, has begun taking orders for the Z10 ahead of making it available in stores next week. Sprint Nextel, No. 3 in the market, won’t sell the Z10 at all. It’s waiting to offer the Q10, a version with a smaller screen and physical keyboard that’s coming out later this year.

BlackBerry splurged on a Super Bowl ad in early February, betting that it could build excitement around the phone even though a U.S. debut wasn’t imminent.

Now that the Z10 is finally here, the key to its success will be how well store salespeople can demonstrate how the phone works to both BlackBerry loyalists and others, said IDC’s Llamas.

“This is an entirely different platform,” he said.

Critics have praised the Z10’s features, including its virtual keyboard. It also lacks a home button, which is used by the iPhone or Samsung Electronics Co.’s Galaxy S to take users back to the main screen. The Z10 relies instead on gesture-driven navigation to switch between applications and peek at messages while still in the Web browser.