Apple's international distribution channel is hard at work to push out the remaining stocks of iPhone 4, iPhone 4S and iPhone 5, purportedly to make room for the upcoming debut of the tech giant's 2013 flagship - the iPhone 5S.

In the United States, giant tech retailer Best Buy offered the iPhone 5S virtually free Friday last week. Buyers simply have to surrender their old but working iPhones to avail of the one-day promo.

Walmart followed suit and dangled the same handset for $US129, which like the Best Buy package comes with a 2-year contract from major U.S. network service providers. While this serving seems less attractive - no free iPhone - Walmart insists what it sells is far better.

This will be the iPhone 5 price tag for the lifecycle of the gadget, or at least until next best thing from Apple crash the scene later this year, which of course is the iOS 7-powered iPhone 5S.

Walmart cut down too the iPhone 4S price to $US39, also on a permanent basis.

Elsewhere in the world, Apple's retail partners are given the green light to start the big 5S push by way of repackaging old iPhone models.

In the Philippines, for instance, Smart Communications, one of the country's biggest telco, bundled the iPhone 4 with a 2-year plan for free. The lock-in period will cost consumers an equivalent of $20 every month.

These underway promos, according to iPhone watchers, will further shift to a high gear once the actual preparation for the iPhone 5S release date kicks in. The cloud of excitement should start descending as early as August, analysts said, or a few weeks prior to the purported D-Day.

That would be in September, basing on projections that were provided by Ming-chi Kuo of KGI Securities and Glenn Yeung of Citi Research.

The duo is also convinced that the iPhone 5S is a significant jump from the previous builds despite widespread assertions that it is merely an incremental update. The focus of the upgrade is CPU and camera capabilities plus the host of killer features the iOS 7 will unleash.