Like clockwork, Reuters has added to the tally of fifth-generation iPhone rumors. Citing three anonymous sources “with direct knowledge of the company’s supply chain,” Reuters claims Apple’s fifth-generation iPhone will have a faster processor, and begin shipping in September.

That means mass production of the phone would have to start no later than August, with an announcement likely to come at Apple’s Worldwide Developers Conference in June.

(By the way, Reuters is fast becoming a regular contributor to the Apple rumor mill; recently it has weighed in on the white iPhone 4, iPad 2, iPad 3.)

Reuters’ report is the latest in a series of rumors about the release date of Apple’s next iPhone. Most rumors about the fifth-generation iPhone have focused on when the official announcement and launch date will be, which may face delays caused by the Japanese crisis.

In case you haven’t been paying close attention, here’s every what various sources have reported about fifth-generation iPhone in the last few months:

On Monday, an analyst from Concord Securities told investors he had heard from unnamed suppliers that the fifth-generation iPhone will only start mass production in September, and come equipped with a faster A5 processor, improved antenna, 8-megapixel rear camera, and Qualcomm baseband. A week before that, Avian Securities also told its investors that Apple won’t begin production until September, pushing back an iPhone 5 launch date to the end of 2011 or early 2012.

From Asia, Taiwanese newspaper DigiTimes added a fresh angle, citing anonymous touch panel suppliers who claimed that Apple won’t release the fifth-generation iPhone this summer because demand for the iPhone 4 has been too strong. Parts shipments have also remained constant, and Apple hasn’t given manufacturers a timeframe for when production of the iPhone 4 will wind down.

Meanwhile South Korea-based ETNews reported last week that unnamed “industry officials” had “confirmed” a June release date for the iPhone, with South Korean carriers KT and SK Telecom starting sales by the end of June.

At the end of March, Japanese-language blog Macotakara.jp reported that Apple was pushing the fifth-generation iPhone release to the fall due to delays caused by the earthquake.

As for the older rumors, Forbes reported last month that Apple will enable mobile payments by embedding near-field communications technology in the fifth-generation iPhone. Then there’s another batch of reports claiming the fifth-generation iPhone will come with an 8-megapixel camera supplied by Sony, which recently made CEO Howard Stringer roll his eyes.