A former top diplomat and Senate Democratic leader said that America's border must be closed and restraints put on uncontrolled immigration.

Former Maine Sen. George Mitchell, a top Clinton fundraiser and former State Department roving mediator, told an audience this week that America has to give up its practice of letting in anybody who wants in.

The Bill and Hillary Clinton ally said that the U.S. should also look at where immigrants are coming from when it sets limits.

"We can not return to a time in our early years when anybody could come here," Mitchell said during a fundraiser for St. Joseph Maronite Catholic Church in Waterville, Maine.

"It's a physical, practical and political impossibility. We have to have reasonable restraints on who can come, from where and how many. No one can rationally argue that we can again open the doors to everyone," he said, according to a report in Kennebec Journal.

Mitchell's warning on open borders, which tracks somewhat with conservatives, carries weight because he remains a leader in the party and among Clinton insiders. He held a fundraiser in April for Clinton, and was State's mediator for the Irish and Middle East peace talks. He is also the co-founder of the influential Bipartisan Policy Center.

Mitchell did not talk about Donald Trump's positions, but said that mistakes in immigration policy have occurred and need to be fixed.

"I believe that our country has benefited from immigration in the past. There have been mistakes and excesses, and we have to correct them and we obviously can not go back to the past when immigration was unlimited," he said in the town he was born in.

"The challenge that comes is how we do it in a way that's fair and in our own interest," he said.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com