U.S. Congresswoman Gabrielle Giffords said Sunday that she will resign her seat this week as she continues 'getting better' from a shooting attack last year.

"I have more work to do on my recovery, so to do what is best for Arizona I will step down this week," Giffords, 41, said on both Twitter and on a video released Sunday on Youtube that was also posted on her website.

Gifford's resignation is expected to take effect on Monday, the Associated Press said Sunday, citing officials in Washington.

In the heavily edited video, Giffords spoke slowly and carefully, smiling and sounding upbeat. 

 "I don't remember much from that horrible day," she said "A lot has happened over the past year. We cannot change that," she said.

"I'm getting better every day. My spirit is high. I will return."

Obama salutes 'inspiration'

Following Gifford's announcement about her resignation, U.S. President Barack Obama praised the Arizona representative, calling her an "inspiration" and "the very best of what public service should be."

Obama said the congresswoman's "cheerful presence will be missed in Washington."

Giffords, a Democrat, was shot point-blank in the head in a shooting rampage on Jan. 8, 2011 while she was at a meet-and-greet event with constituents outside a supermarket in her home district of Tucson.

Six people, including a nine-year-old girl, were killed and a dozen others were wounded in the attack.

Giffords has had a long recovery since, including extensive occupational and physical therapy.

Last November, she said she would not return to her work until she is "better."

This month on the one year anniversary of the shooting, she took part in a candlelight vigil in Tucson.

Jared Lee Loughner has pleaded not guilty to 49 charges in the attack.

The 23-year-old, who has been diagnosed with bipolar disorder, is being forcibly medicated at a Missouri prison facility in an effort to make him mentally ready for trial.