Democratic U.S. Rep. Tammy Duckworth of Illinois announced Monday she's running for U.S. Senate in 2016, setting up a high-profile challenge to Republican Sen. Mark Kirk's re-election bid.

"I'm running for the United States Senate in 2016 because it's time for Washington to be held accountable and to put Illinois' families and communities first," she says in a largely autobiographical video posted Monday to her campaign website. "I will fight my heart out to represent you with honor and integrity."

Duckworth is the first major candidate to throw her hat in the ring for Kirk's seat, and the matchup in Democrat-friendly Illinois could be one of the most competitive nationwide as Democrats battle to regain Senate control.

The Hoffman Estates Democrat is serving a second term in Illinois' 8th District, which covers suburbs west and northwest of Chicago. Duckworth is an Iraq war veteran who served as Assistant Secretary of Veterans Affairs under President Barack Obama. Previously, she was director of the Illinois Department of Veterans Affairs after an unsuccessful bid for Congress in 2006.

Kirk, who won the Senate seat held by Obama in 2010, said through a spokesman Monday that he's served as a "voice for all the people of Illinois."

"Sen. Kirk looks forward to a conversation on the issues that matter most to voters across the state including his proven record of thoughtful, independent leadership, and his work each and every day to serve Illinois families," Kirk spokesman Kevin Artl said. He also noted Kirk's work on cutting spending and taking on the "Veterans Administration for corruption."

Kirk was previously a five-term U.S. representative representing Chicago's suburbs.

In 2012, he suffered a major stroke and underwent many grueling months of recovery learning how to walk and speak, which raised questions about if he would seek a second term. Kirk has said he thinks the stroke raised his profile and that his disability, for which he has to rely on a cane or wheelchair at times, gives him a unique advantage.

Duckworth has also overcome major physical setbacks. In 2004, she lost both legs and part of an arm after the Black Hawk helicopter she was co-piloting was shot down in Iraq. She also relies on crutches or a wheelchair at times.

"I view my time now as a bonus and that has allowed me to speak up without fear," she says in the video where also describes herself as the daughter of a Marine, a wife and a new mom.

She hinted at her platform, mentioning a need for more pre-kindergarten, affordable college loans and a focus on small businesses.

Republicans were quick to pounce on Duckworth's announcement, with Illinois GOP chairman Tim Schneider accusing her in a statement of being a "partisan politician" and "protege" of imprisoned ex-Gov. Rod Blagojevich.

Other Democrats who've indicated interest in running in 2016 include U.S. Reps. Cheri Bustos, Bill Foster and Robin Kelly. Republicans mulling a run include former tea party U.S. Rep. Joe Walsh.