By Sam Oliver

Published: 12:30 PM EST

A flurry of new agreements between Apple and international wireless carriers has given American Technology Research higher conviction in the iPhone's near-term growth prospects, prompting an analyst at the firm to raise his price target on the company for the second time in as many weeks.

"Last week was busy for new carrier agreements," analyst Shaw Wu wrote in a note to clients on Monday. "Vodafone, Telecom Italia, America Movil and Roger Wireless now expect to launch iPhone later this year."

The analyst said the arrangements should more than triple Apple's wireless subscriber opportunity from about 150 million potential customers today to approximately 470 million around the time the handset maker unveils its 3G iPhone.

As a result, Wu bumped his price target on Apple shares for the second time in two weeks to $220, and also raised his forecast for cumulative iPhone shipments by the end of 2008 to 14.6 million from 11 million units.

The change reflects expectations that Apple will ship approximately 11 million iPhones in 2008, or about one million more than the company stated that it hoped to sell over the course of the year. For 2009, the analyst is now expecting the Cupertino-based firm to ship 17 million units, up from his previous estimate of 10 million.

"We continue to believe unlocked iPhones will play an important role in driving sales, but lower than the 55-60 percent contribution we estimated for the December quarter," he wrote. "We see it trending towards 25 percent over the next couple of quarters as more carriers are signed up, particularly in Asia-Pacific."

In a separate report Monday out of investment firm Piper Jaffray, analyst Gene Munster offered a slightly different interpretation of the mass carrier agreements, mainly that they signal an "imminent" release of a 3G iPhone.

"We continue to expect a 3G iPhone to be launched in mid-June. Given the channels are running dry of the current models (8GB and 16GB), the limited availability is one of several indications that the release of a new model is imminent," he wrote.

"We expect the second-generation iPhone to be slightly redesigned with 3G mobile data. Apple's Worldwide Developer's Conference on June 9th is a likely event at which Apple could announce the design and features of the new device."

Munster noted that while the limited availability of iPhones at the online Apple Store and in some retail stores puts pressure on iPhone unit expectations in the June quarter, he believes the release of a new model in June will serve to offset any loss of sales over the next few weeks.

As such, the analyst reiterated confidence in his estimate of 1.7 million iPhone shipments in the June quarter, as well as his Buy rating and $250 price target on shares of Apple.