US Government officials say they fear North Korea could launch a missile today, as the rogue nation celebrates a public holiday.
October 10 in North Korea is celebrated as Party Foundation Day, the day the ruling party of North Korea - now known as the Workers' Party of Korea - was formed in 1945.
An official spoke to Reuters, on the condition of anonymity, saying there had been indications a missile launch could be scheduled, but couldn't reveal any further intelligence.
That comes after a Russian lawmaker, who has just returned from Pyongyang last week, said preparations were underway.
"They are preparing for new tests of a long-range missile," Anton Morozov told Russian media. "They even gave us mathematical calculations that they believe prove that their missile can hit the west coast of the United States.
"As far as we understand, they intend to launch one more long-range missile in the near future and, in general, their mood is rather belligerent."
The claims of an impending launch come as US Defence Secretary James Mattis warned the US Army to "stand ready" for any attack from North Korea.
"There's one thing the US Army can do and that is you have got to be ready to ensure that we have military options that our president can employ, if needed," said Mr Mattis.
In September, North Korea's most recent missile launch cleared Japan, before crashing into the Pacific Ocean.