(CNN) -- North Korea has raised at least one missile into its upright firing position Wednesday, raising concerns that a launch was imminent, a U.S. official told CNN Thursday.
This comes as the world continued to keep watch for a possible missile launch by the secretive regime, and just a day before U.S. Secretary of State John Kerry was due to arrive in the region.
It's not known by the United States why the regime did not proceed with the firing.
The official also also cautioned that the raising of the missile could have been just a trial run to ensure the equipment worked or an effort to "mess" with the United States and the allies which are watching for a launch at any time.
The official declined to specify what type of intelligence led the United States to conclude the medium-range missile -- a Musudan -- was in a firing position.
Pyongyang again threatens to close iconic industrial zone
The North repeated a threat to permanently close the industrial zone it jointly operates with the South, accusing South Korean President Park Geun-hye of putting the manufacturing complex, a key symbol of inter-Korean cooperation, at risk.
The South Korean government, meanwhile, urged Pyongyang to work to resolve the situation through dialogue.
The temporary shutdown of the complex by the North "is not beneficial to the future of the Korean people," South Korean Unification Minister Ryoo Kihl-jae said. "It caused pain to the companies and the workers."
In a sign of the strained relations in the region, North Korea has pulled its more than 50,000 workers out of the Kaesong complex, which is on the northern side of the heavily fortified border that divides the two Koreas, and blocked personnel and supply trucks from entering it from South Korea.
More than 120 South Korean companies have operations there.
In a statement reported Thursday by state-run media, the North Korean government said that what happens at the complex in the coming days "entirely depends on the attitude of the South Korean authorities."
Uneasy calm in the region
The difficulties at the industrial zone are one of the few tangible signs of the tensions between the two sides on the Korean Peninsula.
The U.S. and South Korean militaries are monitoring the movements of mobile ballistic missiles on the east coast of North Korea. And Japan has deployed defense systems, as it had done before North Korean launches in the past, in case any test-fired missile flies near its territory.
But despite the North's barrage of recent threats, which have included warnings to foreigners on the peninsula about their safety in the event of conflict, life is generally continuing as normal in the region.
South Koreans, who have experienced decades of North Korean bombast -- and occasional localized attacks -- have gone about their daily business without alarm.
"South Korea has been living under such threats from the past, and we are always prepared for it," Ryoo, the unification minister, told CNN on Wednesday. He called the current climate "a very ordinary situation."
Tourist visits to the North appear not to have been significantly affected by the situation. China says that while some tour groups have canceled trips, the border between the two countries is still operating normally.
Foreign athletes are expected to compete in a marathon Sunday in Pyongyang, one of many sporting events organized by North Korean authorities to celebrate the 101st anniversary next week of the birth of Kim Il Sung, the founder of North Korea and the grandfather of Kim Jong Un.
"Our group just boarded a full plane for #Pyongyang," Uri Tours, a U.S.-based travel agency that arranges trips to North Korea, tweeted late Wednesday. "Mix of tourists and marathon runners on their way to #NKorea."
In a report that diminished the idea of a nation on the brink of war, the state-run Korean Central News Agency said this week that "the ongoing sports tournaments make the country seethe with holiday atmosphere."
But the United States and its allies say that although much of the North's fiery rhetoric is bluster, they are still taking its threats seriously.
'A dangerous line'
U.S. Defense Secretary Chuck Hagel said Wednesday that North Korea was "skating very close to a dangerous line" after weeks of saber rattling.
"Their actions and their words have not helped defuse a combustible situation," Hagel told reporters at the Pentagon. He said the United States and its allies want to see North Korean rhetoric "ratcheted down," but if that doesn't happen, "our country is fully prepared to deal with any contingency."
American radar and satellites are trained on the east coast of the Korean Peninsula, where North Korea is believed to have prepared the mobile missiles for launch at any time, U.S. and South Korean officials have warned.
Amid the uneasy situation, Kerry will arrive in Seoul from London on Friday to meet with South Korean Foreign Minister Yun Byung-se.
After South Korea, Kerry will visit China and Japan, both countries with large stakes in the Korean crisis.