A missile had been briefly raised to an upright firing position, stoking concerns that a launch was imminent, a U.S. official told CNN on Thursday. Later, another U.S. official said it had been tucked back into its launcher.
In more tough talk from Pyongyang, a government agency was quoted by the state-run media as saying that "war can break out any moment."
After meeting privately with Ban in the Oval Office, President Barack Obama called on North Korea to tone down the rhetoric.
"We agree now is the time for North Korea to end the kind of belligerent approach they have been taking and try to lower temperatures," Obama said during a photo opportunity. "No one wants to see a conflict on the Korean Peninsula."
Ban called on Chinese diplomats to "exercise their leadership and influence" with North Korea to reduce tensions.
U.S. Secretary of State John Kerry, during an upcoming visit, will tell Chinese leaders that Pyongyang is, as one senior administration official said, "putting China's own interests at risk."
The United States wants Beijing to "stop the money trail into North Korea" and to carry a strong message to the North that denuclearization of the Korean Peninsula is China's goal, said the official and a senior State Department official.
The latest move by the North could signify that a much-feared launch is less imminent. It could also mean the government was testing the equipment.
The first U.S. official cautioned that the raising of the missile could have been just a trial run to ensure the equipment works or an effort to "mess" with the United States and the allies that are watching for a launch at any time.
So far, South Koreans -- who've heard the cross-border bombast before -- are taking the swagger in stride. Washington regards much of the North's saber rattling as bluster.
But no one is taking any chances as the daily clamor of threats from North Korean leader Kim Jong Un's government shows no sign of letting up.
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.
The Musudan is an untested weapon that South Korea says has a range as far as 2,175 miles (3,500 kilometers).
It could reach as far as Guam, a Western Pacific territory that is home to U.S. naval and air bases, and where the United States recently said it was placing missile defense systems.
The United States and South Korean militaries have been monitoring the movements of mobile ballistic missiles on the east coast of North Korea. Japan has deployed defense systems.
Mike Rogers, chairman of the House Intelligence Committee, told CNN on Thursday that Kim is using rhetoric to solidify his base within his country and its military.
"North Korea is one of those countries that's an army with a country, not a country with an army," said Rogers.
The mood in South Korea? 'Very ordinary'
Life is generally continuing as normal in the region, however, 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.
South Koreans, who have experienced decades of North Korean rage and posturing -- and occasional localized attacks -- have gone about their daily business without alarm.