Presumptive Republican presidential nominee Donald Trump is once again calling for a temporary ban on Muslim immigrants entering the U.S., but a GOP congressman from central New York isn't sure that's constitutional.

U.S. Rep. John Katko said Monday that Trump's plan may not "pass constitutional muster."

"You're talking about banning whole races of people or whole ethnic origins of people," Katko, R-Camillus, said in a phone interview. "I'm not sure that's what we do as a people."

Trump repeated his call for such a ban on Monday one day after an attack at an Orlando nightclub left 49 dead and 53 wounded.

The shooter was born in New York, but his parents were immigrants from Afghanistan.

Trump said if he's elected president, he will "suspend immigration from areas of the world when there is a proven history of terrorism against the United States, Europe or our allies, until we understand how to end these threats."

He insists the ban would be temporary. It will be lifted, he said, "when we as a nation are in a position to properly and perfectly screen those people coming into our country."

Katko, though, is skeptical.

"Obviously the idea is to ferret out those that we think are dangerous," he said. "If we don't know enough about someone's background, we shouldn't let them into the U.S. That was my concern with the Syrian refugees.

"If we can't verify where people come from and verify that they're not a threat risk, they shouldn't come here. But by banning whole groups of people based on their ethnic origin it's just not what we're about as a country."

Trump's plan does have some support from voters.

A Rasmussen poll released in December after Trump initially proposed the idea of temporarily banning Muslims from entering the U.S. found 46 percent of voters support the concept.

A more recent poll conducted by Morning Consult found 50 percent of voters support Trump's plan.