The United States urged North Korea on Tuesday to refrain from another missile test after South Korea warned that the communist nation appears to be preparing to test its Musudan intermediate-range ballistic missile after four successive failures.

"We, of course, would have concerns if the North Koreans were to conduct another missile test. It would be another violation of U.N. resolutions. It would be another provocative action," Pentagon press secretary Peter Cook said at a regular press briefing. "So we certainly would urge North Korea to refrain from doing that sort of thing. We continue to closely coordinate with our allies in the region about the situation and we're watching it very, very closely."

Earlier in the day, South Korean officials said the North was showing signs of deploying a mobile launcher to its east coast in an attempt to fire a Musudan missile believed to be capable of reaching the U.S. territory of Guam.

Seoul's Joint Chiefs of Staff also said the military is closely tracking related signs.

So far, North Korea has attempted to test-fire the Musudan missile four times -- first on April 15, two more on April 28 and the latest on May 31 -- but all ended in failure, with the missile exploding in midair or on a mobile launcher or crashing seconds after launch.

The U.N. Security Council condemned the launches as violations of council resolutions.

State Department spokesman John Kirby also urged the North to stop provocative acts.

"This is the time for the DPRK to stop the provocations to work toward stability on the peninsula," he said. "These kinds of actions, if and when it happens again, do nothing to increase the security on the peninsula and fly in the face of their international obligations."

Meanwhile, Cook said the U.S. is doing everything it can to protect its forces around the world, after South Korea's main intelligence agency reported that the militant group Islamic State designated U.S. Air Force facilities and a South Korean national as targets of attacks.

The National Intelligence Service said earlier this week that the U.S. air bases in Pyeongtaek and Gunsan were among 77 U.S. and NATO facilities mapped recently by IS on the internet messenger program Telegram.

"Force protection around the world is of critical importance to us and we will continue to do everything we need to protect our forces, whether it be in South Korea, or other parts of the world, from not only the threat from ISIL but from other threats," Cook said.

"So this is something that we would work very closely, of course, with the South Korean government to address any concerns that are there, but force projection is job one for us and was even before this report came from the South Korean government," he said. (Yonhap)