SIOUX CITY, Ia. — Campaigning in Iowa on Sunday, U.S. Sen. Bernie Sanders sought to distinguish his legislative record from that of former Vice President Joe Biden.

At a town hall event in Spencer, a woman in the crowd told the Vermont senator that she was trying to decide between Sanders and Biden.

"I like what I heard today," she said at the Clay County Regional Events Center. "How are you different than Biden?"

Sanders smiled and promised to "answer that in a couple ways."

As he has done since his first Iowa campaign trip in March, Sanders pledged to support the eventual Democratic nominee and promised to avoid "ugly personal attacks" throughout the presidential primary process.

"What we have got to show the world is that we can run a serious primary process without trying to destroy each other," he said.

Still, the senator went on to point out major policy distinctions with Biden:

He said international trade agreements have been "disastrous" for American workers and farmers, particularly pointing to NAFTA and the United State's agreement to normalize trade relations with China. "I led the effort against those trade agreements," Sanders said. "Joe voted for them."

Echoing his critique of Secretary of State Hillary Clinton from the 2016 contest, Sanders also held up the vice president's vote to authorize the war in Iraq, which he said was one of the most significant Congressional votes in recent years. "I voted against it," he said. "Joe voted for it."

Sanders also pointed out the vice president's vote to deregulate Wall Street by supporting the Gramm-Leach-Billey bill in 1999. "I voted against it," Sanders said.

Sanders wrapped up his comments about Biden by calling the vice president a "very decent guy."

"He is a friend of mine," the senator said. "We have differences of opinion and you all will make your own decisions."

The back-and-forth between the two Democratic front runners has been brewing for days.

Biden, campaigning in Monticello on Tuesday, said he was proud of his legislative record, though he declined to comment on Sanders' previous criticism of his voting record in the U.S. Senate.

"I'm going to have plenty of time to respond to that," he said. "I'm not going to get into debates with my colleagues here. We'll have plenty of time on the stage. I'm proud of my record."

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It was the second time Sanders has drawn a distinction with the former vice president during his most recent Iowa campaign swing.

In an interview with ABC News that aired Sunday morning, Sanders said he disagreed with Biden's earlier claim that he touted "the most progressive record" among the field of 2020 Democratic candidates.

"I think if you look at Joe’s record and you look at my record, I don’t think there’s much question about who’s more progressive," Sanders told ABC Chief White House Correspondent Jonathan Karl on Saturday morning before shaking hands and meeting hundreds of supporters at the Downtown Farmers' Market in downtown Des Moines.