"You're never going to reach perfection," the Maine independent said on CNN's "New Day." "If we have to wait until we are satisfied that the system is absolutely perfect, any system, then you wait forever. I suppose Donald Trump might say, 'That's okay,' but that would be a terrible loss for this country."
this summer his blanket ban on immigrants to the US to include those "from any nation that has been compromised by terrorism."
"You have many, many groups, because we're allowing these people to come into our country and destroy our country and make it unsafe for people," Trump said Monday on "Fox and Friends," arguing that the stricter immigration policies he has proposed would better protect the US from terror.
But King, who normally caucuses with Democrats in the Senate and endorsed Hillary Clinton in July
, said such a ban could prevent "thousands and thousands" of immigrants from contributing to the greatness of America.
"You've got the bad guys, but you've also got thousands and thousands of really good people who come into this country -- everybody from Einstein to Donald Trump's ancestors to mine and yours came in through the immigration system," King told CNN's Alisyn Camerota.
But being an open country doesn't mean that the US government should loosen its vetting process, King said.
"That doesn't mean that we relax or we stop, but to say that the system has got to be perfect before we do anything, I just don't think is realistic," he said.
The man who stabbed nine people at a Minnesota mall Saturday before being shot dead by an off-duty police officer was a "soldier of the Islamic state," according to an ISIS-linked news agency. Local reports identified him as being of Somali descent.
Rep. Keith Ellison, who is Muslim, said following terrorist attacks the Minnesota Islamic community becomes concerned about rising Islamophobia.
"We know there will be some people that are going to take the bait of the terrorists and say 'This is about the Muslim community, the Somalis or the immigrants.' And it's not about that," the Minnesota lawmakers said on CNN's "New Day."
Ellison said the best response to terrorism acts is for America to unify instead of becoming divisive.
"The answer really is to come together as a community to be vigilant, to share information and to never let them forget who we are and what we're about," he told CNN's Chris Cuomo. "America is a pluralistic, inclusive society. We're not going to stop being that because some horrible person decided to commit an atrocious act."