WASHINGTON (Reuters) - Pete Buttigieg, the Democratic mayor of South Bend, Indiana, launched an underdog 2020 bid for the White House on Wednesday, aiming to stand out as a problem-solving Midwestern outsider who would be the first openly gay nominee of a major U.S. political party.

The relatively unknown Buttigieg, 37, a two-term mayor of the Rust Belt city of about 100,000 people, said he represented a new generation of leadership with fresh approaches to the country’s problems.

In an email and video to supporters, he offered a sharp contrast to Republican President Donald Trump’s nostalgia-driven message invoking an America of the past.

“My generation is the generation that experienced school shootings beginning when I was in high school, the generation that fought in the post-9/11 wars, the first generation to have to deal with the reality of climate change, and the first generation not to be better off than our parents materially - if nothing changes,” Buttigieg said.

“Only a forward focus - untethered from the politics of the past and anchored by our shared values - can change our national politics and our nation’s future.”

Buttigieg enters what is expected to be a crowded Democratic field of candidates vying for the right to challenge Trump, the likely Republican presidential nominee, in 2020. The mayor formed an exploratory committee to begin raising money and hiring staff to compete for the Democratic nomination.

He will face a tough task raising funds and building a coalition of support in a race that will feature many candidates with greater name recognition and bigger donor networks.

Other Democratic rivals for the nomination include U.S. Senators Elizabeth Warren of Massachusetts, Kamala Harris of California and Kirsten Gillibrand of New York, as well as U.S. Representative Tulsi Gabbard of Hawaii and former San Antonio mayor and U.S. housing secretary Julian Castro.

Speaking to reporters in Washington, where he was attending a national mayors conference, Buttigieg acknowledged the odds but touted his unique candidacy.

“When it comes to experience right now, nothing could be more relevant than leading one of America’s turnaround cities,” he said.

“I belong to a party whose characteristic has always been to look for fresh voices, new leadership and big ideas, and I think that’s what 2020 is going to be about.”

As mayor of South Bend, a blue-collar town that is home to the University of Notre Dame, Buttigieg made redevelopment a top priority and was named mayor of the year in 2013 by the website GovFresh.com. He signaled his White House run in December when he announced he would not seek a third term as mayor.

Republicans dismissed Buttigieg’s candidacy as a waste of time and said he should focus on South Bend’s problems.

“His bid isn’t just bad news for residents, it’s more proof that Democrats are about to endure the most crowded, divisive, and contentious primary in history,” said Republican National Committee spokesman Michael Ahrens.

Buttigieg began building a national profile in 2017 with an unsuccessful run for chairman of the Democratic National Committee. Former President Barack Obama mentioned him in an interview shortly before leaving the White House as a young Democrat with a bright future.

The Harvard graduate and former Rhodes Scholar returned to his hometown of South Bend and was elected mayor in 2012 at the age of 29. He served a seven-month Naval Reserve tour in Afghanistan while mayor and came out as gay in a 2015 column for the local newspaper. He married in June 2018.