By I-Hsien Sherwood (i.sherwood@latinospost.com) | First Posted: Apr 27, 2013 10:47 AM EDT

The Samsung Galaxy S4 is finally officially available in the United States -- AT&T retail stores are carrying the phone beginning today for $199.99 with a two-year contract.

In addition, online sales begin today at Sprint. The Galaxy S4 costs $249.99 with a two-year contract, though Sprint is offering a $100 discount if you port over a phone number from another carrier, so Sprint loyalists are out of luck.

If you're planning on grabbing the Galaxy S4 in person today, call ahead to the AT&T store first. Samsung is dealing with a global supply shortage, and many of the other carriers have pushed back their release dates because of a lack of inventory.

Sprint stores won't have the Galaxy S4 in stock for the foreseeable future. T-Mobile online sales begin on Monday, but retail stores will need to wait another one or two weeks, depending on location. Verizon doesn't get the Galaxy S4 for another month.

The shortage is likely caused by a lack of RAM. Samsung produces half of the world's DRAM, used in smartphones and tablets, but its had to purchase additional units from competitor SK Hynix to meet demand for the Galaxy S4.

Last year, U.S. carriers had to deal with a similar delay in the launch of the Galaxy S3, but Samsung's precautions this time around seem to have been ineffective.

The Samsung Galaxy S4 features a 1.6GHz eight-core Exynos 5 Octa processor or a 1.9GHz quad-core Qualcomm Snapdragon 600 processor (depending on country), 2GB of RAM, a 5-inch 1920x1080 Full HD AMOLED display at 441 ppi, a 13-megapixel rear-facing camera with 1080p HD video, a 2-megapixel front facing camera, internal storage between 16 and 64GB, an SD card slot that can accommodate an additional 64GB, a polycarbonate body, Smart Pause and floating touch tech and runs Android 4.2.2 Jelly Bean.

Check back for the latest info on the Galaxy S4 as it becomes available.

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