A 13-year-old boy armed with a loaded gun and enough bullets to start a small war was nabbed in the Port Authority Bus Terminal, cops said Saturday.

The runaway, who had gotten off a Greyhound bus from rural southwest Virginia at about 5:30 p.m. Friday, told PA Police officers it was his first visit to New York and he believed he would need protection.

The youth, whose name was withheld because of his age, said someone he knows had given him the gun, a .40-caliber Glock with nine rounds of ammo in the magazine, as well as 79 extra .40- and .45-caliber bullets he had in a box.

Police had gotten a tip and were waiting for him.

He told his reception committee, “The gun is in my bag,’’ cops said.