White House claims N. Korea sanctions are working

Even as the North Koreans tested four more missiles this week, the White House said Thursday that tough new United Nations sanctions are showing signs of working.

White House press secretary Robert Gibbs declined to say what evidence the administration has that the most recent round of sanctions was effectively tightening the noose on North Korea, and he warned that it will likely continue with provocative behavior.

"I think it is clear the sanctions are having an impact," Gibbs said.

When asked what the U.S. was doing in response to the most recent round of threats and missile tests from the country, Gibbs said "first and foremost, the administration is working to ensure the vigorous implementation of those sanctions."

"We continue to watch the North Koreans," Gibbs said. "They continue to do and say what they do and say."

The Thursday test-firing of four short-range, surface-to-ship missiles came two days after a North Korean vessel, believed to be carrying weapons or weapons materials in defiance of the sanctions and being followed closely by the USS John S. McCain, turned around and headed back to North Korea.