DETROIT (Reuters) - U.S. Democratic presidential rivals Joe Biden and Kamala Harris expressed frustration on Thursday with a debate format they said left them little time to explain their views and led to the combative exchanges featured in the first two debate rounds.

Democratic 2020 U.S. presidential candidates (L-R) U.S. Senator Michael Bennet, U.S. Senator Kirsten Gillibrand, former HUD Secretary Julian Castro, U.S. Senator Cory Booker, former Vice President Joe Biden, U.S. Senator Kamala Harris, entrepreneur Andrew Yang, U.S. Rep. Tulsi Gabbard, Washington Governor Jay Inslee and New York City Mayor Bill de Blasio pose together before the start of the second night of the second U.S. 2020 presidential Democratic candidates debate in Detroit, Michigan, July 31, 2019. REUTERS/Lucas Jackson

The day after a televised debate marked by a series of attacks on her record, Harris said the brief chances to talk - each candidate in Wednesday night’s debate in Detroit was limited to 60 seconds to answer a question and 30 seconds to rebut an attack - allowed no real exploration of policy.

“It can be a frustrating process. There are so many of these issues that cannot be captured in 60 seconds,” Harris, a U.S. senator from California, told reporters. “It is a process that is conducive to sound bites.”

Biden, the former U.S. vice president and the Democratic front-runner, who came under withering attack over healthcare, immigration and criminal justice reform in the debate, said it was difficult to explain complicated topics in less than one minute.

“That’s not a debate. I understand why it has to be that way, but I’m looking forward to getting to a place where we can actually exchange ideas,” he told reporters after visiting a diner in Detroit.

The crowded field of more than two dozen candidates vying for the Democratic nomination to challenge Republican President Donald Trump in 2020 has forced the party to set up back-to-back nights of debates featuring 10 candidates each. That has led to rapid-fire exchanges that frustrated not only candidates but some viewers.

Republican Mike Huckabee, a former presidential candidate, complained about the “game show rules” of the debate. “These people are trying to be president - not win a Buick!” he said on Twitter.

The party’s next debate is not until September, and the Democratic National Committee has doubled the fundraising and polling requirements to qualify for participation in an effort to reduce the crowd on stage.

Biden and Harris said they were not surprised they were the target of attacks from all directions during the debate.

“If you’re considered a front-runner, you should be prepared to take a hit. So there was nothing about last night that surprised me,” Harris said.

But Biden said it was “absolutely bizarre” that the immigration and healthcare policies of former President Barack Obama, still the most popular figure in the Democratic Party, came under sharp criticism during the debate.

“I hope in the next debate we can talk about how we can fix the things that Trump has broken, not how Barack Obama made all these mistakes, because he didn’t,” said Biden, who served as vice president under Obama for eight years. “This, going back 10, 20 or 30 years, is just a game to make sure we hand the Republicans an election,” he said.

Harris and Biden clashed early in the debate over their healthcare plans. Harris criticized Biden for leaving too many people uninsured under his proposal, and Biden ridiculed the idea that Harris’ plan would not require a middle-class tax hike.

“It’s a complicated issue when you get into the details, so obviously a debate where you can only talk for seconds is not the best venue to actually describe the detail,” Harris said on Thursday.

Cory Booker, a U.S. senator from New Jersey who clashed with Biden in the debate on their criminal justice records, told a rally in Detroit Thursday night that the strife would eventually be forgotten.

“We may be having a primary debate right now, but we know we are going to close ranks behind the candidate,” he said.