Lumia 800, which Nokia's best high-end smartphone and is the fruit of its partnership with Microsoft, is rumored to hit the U.S. market in January. It will, however, face immense pressure from LG Nitro HD, which has more specifications.

Lumia 800 has been cleared for sale in the U.S. by the Federal Communications Commission (FCC). While the organization's documents are less than forthcoming about the carrier for Lumia 800, its little brother, Lumia 710, is headed to T-Mobile. The 800 lacks a 1700 MHz AWS radio, meaning it will not join the 710's Jan. 11 launch on T-Mobile, according to the FierceWireless.

Meanwhile, Nokia released its first software update for Lumia 800 Dec. 8. The phones are powered by the Windows Phone 7.5 Mango operating system.

The Nokia phone features a 3.7-inch AMOLED display that blends seamlessly into the reduced body design and has a 1.4 GHz processor. Nokia Lumia 800 contains an instant-share camera experience, based on leading Carl Zeiss optics, HD video playback, 16GB of internal user memory and 25GB of free SkyDrive storage for storing images and music.

On the other hand, LG Nitro HD, which was made available on AT&T's network from Dec. 4, has a dual-core 1.5 GHz Scorpion processor, 4.5-inch True HD AH-IPS display, 1 GB of RAM, 4GB of internal memory plus an included 16GB microSD card, an 8-megapixel rear-facing LED flash camera with 1080p video capture and a secondary front-facing camera for video calls. It runs on Google Inc.'s Android 2.3 Gingerbread OS.

Taking advantage of LG's new proprietary True HD technology, Nitro HD's 4.5-inch AH-IPS (Advanced High-Performance In-Plane Switching) display supports resolutions up to 1280 x 720 pixels and offers unrivaled color accuracy, brightness, battery efficiency and performance.

LG said Nitro HD's 500 nit display luminance allows for clear viewing in direct sunlight and RGB stripe pixels deliver incredibly accurate true-to-life color rendering. The phone is the first smartphone in AT&T's portfolio with a true high definition screen and is the third 4G LTE smartphone for AT&T customers.

Let's look at the specifications of LG Nitro HD vis-à-vis the Nokia Lumia 800.

Display: Nitro HD touts a 4.5-inch True HD AH-IPS (Advanced High-Performance In-Plane Switching) capacitive touch-screen with 1280 x 720 pixels resolution at about 326 ppi pixel density. On the other hand, the Lumia 800 sports a 3.7-inch AMOLED ClearBlack curved display with a resolution of 800 x 480 pixels at 252 pixels per inch (ppi) density.

Size: Nitro HD comes with 133.9 x 67.8 x 10.4 mm dimensions and weighs 127 grams while Lumia 800 has 116.5 x 61.2 x 12.1 mm dimensions and weighs 142 grams.

Processor: Nitro HD features 1.5GHz Scorpion dual-core processor, Adreno 220 GPU, Qualcomm APQ8060 processor with 1GB RAM. On the other hand, Lumia 800 packs a 1.4GHz Scorpion CPU, Adreno 205 GPU, Qualcomm MSM8255 Snapdragon chipset with 512MB RAM.

Camera: Both smartphones sport rear-facing 8 megapixel cameras. Nitro HD has 3264x2448 pixels, autofocus, LED flash in the rear camera with 1080p video capture capability; Lumia 800's has 3264x2448 pixels, Carl Zeiss optics, autofocus, dual-LED flash with 720p video capture. The former has an additional 1.3-megapixel front-facing camera for video calling while the Lumia doesn't have one.

3G/4G: Nitro HD has HSDPA 21 Mbps, HSUPA 5.76 Mbps and supports 4G LTE while Lumia 800 has HSDPA 14.4 Mbps and HSUPA 5.76 Mbps.

Operating System:  Lumia 800 runs on Microsoft's Windows Phone 7.5 Mango operating system. On the other hand, Nitro HD has Android 2.3 Gingerbread operating system with both promised Google Inc.'s latest smartphone OS, Android 4.0 Ice Cream Sandwich.

Ice Cream Sandwich is a combination of Gingerbread and Honeycomb in one unit. Android's Head of Engineering, Mike Claren, announced the new OS as Google's most ambitious release to date. The newest features include widgets in a new tab, a customizable launcher, Gmail with offline search with a two-line preview and new action bar at the bottom, better voice integration, improved copy and paste and a new tabbed Web browser that allows up to 16 tabs.

WLAN/Bluetooth/USB: Nitro HD has Wi-Fi 802.11 b/g/n, Wi-Fi Direct, DLNA, Wi-Fi hotspot, Bluetooth 3.0 version with A2DP, HS, and microUSB 2.0 version. On the other hand, Lumia 800 has Wi-Fi 802.11 b/g/n, Bluetooth 2.1 version with A2DP, EDR and microUSB 2.0 version.

Storage: Nitro HD has fixed 4GB internal storage with a 16GB microSD card included in the package that can be expanded up to 32GB. On the other hand, Lumia 800 comes with 16GB internal memory and lacks an external memory slot.

Battery: Nitro HD comes with a standard Li-ion 1830 mAh battery. Lumia 800, on the other hand, has a 1450 mAh BV-5JW Battery that is expected to give talk time of up to 13 hours on 2G network and 9.5 hours on 3G and standby of up to 335 hours on 2G and 265 hours on 3G.

Pricing: The estimated retail price for Lumia 800 will be about $595 excluding taxes and subsidies while Nitro HD is priced at $149.99 with a two-year AT&T contract in selected areas.