The South Korean government kept quiet Thursday about media reports of a North Korean missile launch this week.
South Korean media quote unnamed officials as saying North Korea launched two short-range missiles Wednesday morning local time near its border with China. It is not clear if the launch was a test or a mistake.
South Korea - which has a policy of engaging the communist North as a way to better relations - is hesitant to publicly criticize Pyongyang.
But the reports drew a quick response from Washington. U.S. State Department Spokesman Sean McCormack said the reported launches are a source of concern.
"North Korea's missile program and activities are a threat, not only to the region, but the international community at large," he said. "We are working with our friends and allies in the region on deployment of active missile defenses."
North Korea test-fired a long-range missile over Japan in 1998 - alarming the international community. But Pyongyang has not conducted any medium- and long-range missile tests since. North Korea is also believed to be one of the world's largest exporters of missile technology.
In U.S. Senate testimony this week, the Commander of U.S. Forces in Korea, General Burwell Bell, warned North Korea has 200 mid-range missiles capable of reaching Japan. He said Pyongyang might have long-range missiles capable of reaching the continental U.S. within the decade.
The timing or purpose of this week's reported North Korean launch is not clear.
But Kim Tae-woo - an analyst at Seoul's Korea Institute for Defense Analyses - says it was probably just part of regularly scheduled short-range missile drills.
"Even North Koreans themselves will believe that [this] is a minor thing and nobody will think it serious," said Kim. "If North Korea tested a large-size [long range] missile, that could be interpreted differently."
Kim says he and his colleagues are more concerned about newly emerging reports that North Korea may be selling long-range missile technology to Iran - which is also embroiled in a dispute with the international community over its nuclear programs.
"That development could be really serious," added Kim. "That could prompt a response from the U.S. If that is true, it is a really serious development."
This week's reported launch comes within 24 hours of Pyongyang's latest announcement that it will not return to multinational talks aimed at ending its nuclear weapons programs. Three years of negotiations have not produced any progress on the issue.
North Korea says it has nuclear weapons, but has never conducted a nuclear test. U.S. intelligence officials have expressed doubt Pyongyang has the technology to mount a nuclear device on a missile and fire it accurately. However, they fear North Korea may export nuclear and missile materials and technology to nations or groups hostile to the United States.