South Korea is sharply tightening security at the U.S. ambassador's residence in Seoul after a recent break-in by college protesters.
The Seoul Metropolitan Police Agency says it's dispatching 80 more officers to the area.
It's also setting up a hotline that will enable officers to be deployed more quickly in emergencies.
The police have requested arrest warrants for 7 of the 17 students who used ladders last Friday night to climb over the wall of the residence.
They were protesting Washington's demand that Seoul pay more for the cost of stationing U.S. troops in South Korea.