Vice President Kamala Harris speaks on immigration at a campaign event in Douglas, Ariz., on Friday. Justin Sullivan/Getty Images

Shortly after touring the Mexican border in swing state Arizona on Friday, Vice President Kamala Harris took the fight over immigration straight to Donald Trump, laying blame on the former president for scuttling a bipartisan border security bill.

Harris, in her first visit to the border since becoming the Democratic presidential nominee, took a tougher line on border security than her boss, President Joe Biden, calling for tightening asylum restrictions as she attempts to blunt Trump's lead on the polls on immigration, one of the top issues in this election.

"I reject the false choice that suggests we must choose either between securing our border and creating a system that is orderly, safe and humane," Harris said, CNN reported. "We can and we must do both."

But she also held Trump responsible for killing the border security deal negotiated by Republican Sen. James Lankford of Oklahoma and Democratic Sen. Chris Murphy of Connecticut.

"It was the strongest border security bill we have seen in decades. It was endorsed by the Border Patrol union. And it should be in effect today, producing results in real time, right now, for our country," she said in the border town of Douglas, Ariz.

"But Donald Trump tanked it. He picked up the phone and called some friends in Congress and said, 'Stop the bill,'" she continued.

"He prefers to run on a problem instead of fixing a problem. And the American people deserve a president who cares more about border security than playing political games and their personal political future," she said.

Trump at a campaign event in Michigan returned fire against Harris, saying she is responsible for the "horrors" committed by illegal immigrants into the United States.

"She unleashed these atrocities, and blood is on her hands at a level that, probably, nobody's ever seen in this country," he said.

The former president is expected to continue to battle Harris on immigration during an appearance in Wisconsin Saturday at the center of a controversial case involving a Venezuelan migrant accused of sexually assaulting a woman and attacking her daughter earlier this month.