(YouTube)

Arizona Congresswoman Gabrielle Giffords will step down from the House this week to focus on he recovery from a gunshot wound to the head, but she vowed in a two-minute video announcement of her decision that she will be back.

"I have more work to do on my recovery and so to do what is best for Arizona I will step down this week," she said in the video, which was posted on her website and on YouTube. "I'm getting better every day. My spirit is high. I will return and we will work together for Arizona and this great country."

Giffords has made a stunning recovery after being shot in the head by a gunman who opened fire while the Arizona congresswoman was meeting with constituents at a suburban Arizona supermarket in January 2011. Six people were killed and besides Gifford, 12 others were wounded in the shooting rampage Jan. 8, 2011.

The bullet entered Giffords' head just over her left eye and traveled through the left side of her brain. In an interview with ABC News' Diane Sawyer 10 months after the shooting, husband Mark Kelly said: "It's clear that any lower, it would've killed her, any further midline, it would've killed her. If it crossed hemispheres, it would've killed her. Any further outboard, she'd never be able to speak again. Any higher, she'd never be able to walk."

By November 2010, Giffords had regained her ability to speak, thanks to a grueling course of speech and physical therapy. But she was still struggling with aphasia, which was shown in the home videos Kelley shot during her rehabilitation.

She said in the video today that she needs to focus on her rehabilitation.

"Thank you for your prayers and for giving me time to recover," she says, speaking clearly but slowly and haltingly, her eyes bright and focused.

Before leaving office, Giffords will complete the "Congress On Your Corner" event that was interrupted last January when 22-year-old gunman Jared Loughner opened fire, killing six and wounding twelve.

Giffords, a Democrat, also plans to attend President Obama's State of the Union address Tuesday.

In a statement today, House Minority Leader Nancy Pelosi said Giffords has been "an inspiring symbol of determination and courage to millions of Americans."

"Gabby's message of bipartisanship and civility is one that all in Washington and the nation should honor and emulate," Pelosi said in the statement. "I join all my colleagues in Congress in thanking Gabby for the honor of calling her colleague and wishing Gabby and Mark great success and happiness. She will be missed in the House of Representatives, but her legacy in the Congress and her leadership for our nation will certainly continue."

Full statement from Giffords:

"Arizona is my home, always will be. A lot has happened over the past year. We need to not change that but I know on the issues we fought for we can change things for the better. We can do so much more by working together. I don't remember much from that horrible day but I will never forget the trust you placed in me to be your voice. Thank you for your prayers and for giving me time to recover. I have more work to do on my recovery and so to do what is best for Arizona I will step down this week I'm getting better every day. My spirit is high. I will return and we will work together for Arizona and this great country."

Fellow Arizona Democrat, Rep. Raul Grijalva, said he was surprised Giffords resigned.

"I thought she would just see how the recovery proceeded, but I guess she decided in her own mind that this recovery is number one and that's the right decision for her," he said.

Grijalva said he hopes to see Giffords return to work one day.

"She will fully recover and when she decides to come back from her pause to take care of herself, she'll pick up where she left off, there's no question about that," Grijalva said. "I'm looking forward to seeing her, thanking her, wishing the best and letting her know we're going to keep the seat warm for her."