Gov. Christie has joined the chorus of governors saying their states will not accept Syrian refugees.

In a letter sent Tuesday to President Obama, Christie said, "I cannot allow New Jersey to participate in any program that will result in Syrian refugees – any one of whom could be connected to terrorism – being placed in our State." That line was identical to language used by at least one other Republican governor, Texas Gov. Greg Abbott, in pledging to reject Syrian refugees in the wake of the recent terrorist attacks in Paris.

Christie said he had directed the New Jersey Department of Human Services not to participate in the resettlement of Syrian refugees. He asked nongovernmental organizations to notify state officials of their placement of any Syrian refugees in New Jersey.

The governor, a Republican presidential candidate, also in the letter urged Obama "to halt your plans to accept more Syrian refugees in the United States. I have no doubt that ISIS will try to exploit American humanitarianism to expose Americans to similar risk."

More than half of U.S. governors – nearly all of them Republicans – have said they oppose accepting Syrian refugees in their states. Experts say states have limited authority over refugee resettlement.

A person gains refugee status under federal law, and a state "has absolutely no legal authority to restrict or bar that person from entering the state," said Gregory Chen, director of advocacy for the American Immigration Lawyers Association.

If governors wanted to "set up checkpoints at state lines or airports, I guess they could do that," Chen said. But such actions "would be immediately subject to a lawsuit."

This year, 75 Syrian refugees have been resettled in New Jersey, according to data compiled by the U.S. State Department.

All refugees are extensively screened before entering the U.S., according to State Department officials, including fingerprint and biographic checks and an in-person overseas interview. Officials say the average screening process takes 18 to 24 months.

Christie told a conservative radio host Monday he didn't trust the administration's ability to vet Syrian refugees, and "so I would not permit them in" – a harder line than earlier this fall, when he had said the U.S. might need to accept some.

"What about orphans under the age of 5?" asked the host, Hugh Hewitt.

"You know, Hugh, we can come up with 18 different scenarios," Christie said. He said "appropriate vetting" was needed, "and I don't think orphans under 5 should be admitted into the United States at this point. They have no family here. How are we going to care for these folks?"

He drew a sharp attack Tuesday from New York City Mayor Bill de Blasio – often a verbal sparring partner of Christie's – who said that given Christie's standing as an elected official, "his comment is an embarassment to this country."