NEW YORK (AP) — The city and the United Nations, which have tussled for years over parking tickets and property taxes, are now squabbling over schoolchildren — specifically, whether it's safe for them to visit U.N. headquarters.

The nation's largest school system said this week it was halting trips to the landmark complex over concerns about fire hazards, though the U.N. insists the buildings are safe.

"We feel that it's very unfortunate that children in this area — in the host city, in our neighborhood — can't come visit," U.N. spokeswoman Soung-ah Choi said Wednesday.