DEERFIELD — Gov. Scott Walker said Friday that he is not entirely opposed to Wisconsin providing temporary shelter for unaccompanied children coming across the Mexican border, but he is concerned they would linger in the U.S. and eventually "drain the entire system."

The city of Madison has proposed two sites to house some of the tens of thousands of children fleeing from gang violence in Honduras, Guatemala and El Salvador. The federal government also has asked officials in the Milwaukee area to do a location search.

Fifty children have already been placed with families in Wisconsin. The federal government is seeking temporary shelter for others until they can be reunited with relatives or family friends or returned to their home countries.

Walker said he has joined other governors in signing a letter expressing concern about the children's safety, border security and the strain on state resources.

"If we're not having a rapid process to get back to the country of origin, they're going to basically blend into whatever community and state and country they're in," Walker told reporters after a campaign stop in Deerfield. "That's going to have costs and drain the entire system."

But the Republican governor said he also hasn't "done a blanket opposition" to the children coming to Wisconsin.

"We've just raised a number of concerns," he said.

Walker spoke a day after Republican Assembly Speaker Robin Vos said Wisconsin should not be considered a site to temporarily house the children. Vos and other state lawmakers sent a letter to Department of Homeland Security Secretary Jeh Johnson saying it would be in the children's best interests if they were kept near the United States' southern border, so families can be promptly reunited.

Ken Wolfe, a spokesman for the U.S. Department of Health and Human Services, said it is seeking proposals for a wide range of possible places to shelter the children, but only a few will ultimately be chosen.