* Missile fired from site of N.Korean sub base - S.Korea
* Trump, China's Xi set to discuss N.Korea at upcoming summit
* N.Korea has conducted numerous missile tests in recent months
SEOUL - North Korea fired a ballistic missile on Wednesday from its east coast into the sea off the Peninsula, South Korea's military said, ahead of a summit between U.S. and Chinese leaders who are set to discuss Pyongyang's arms program.
The launch was from Sinpo, a port city on the North's east coast, and the missile flew about 60 km (40 miles), South Korea's Office of the Joint Chiefs of Staff said in a short statement. Sinpo is the site of a North Korean submarine base.
The launch comes just a day before the start of a summit meeting between U.S. President Donald Trump and China's President Xi Jinping, where talks about adding pressure on the North to drop its arms development will take centre stage.
Any launch of objects using the ballistic missile technology is a violation of U.N. Security Council resolutions but the North has defied the ban as infringement of its sovereign rights to self defense and the pursuit of space exploration.
North Korea attempted to launch a ballistic missile two weeks ago from its east coast and earlier in March fired four missiles towards Japan, some of which came as close as 300 km (190 miles) to its coast.
The reclusive state has also conducted two nuclear weapons tests since January 2016.
The U.S. military's Pacific Command said initial assessments indicated the launch was of a KN-15 medium-range ballistic missile, which would be the same kind North Korea test-launched in February.
The North is believed to be developing an intercontinental ballistic missile (ICBM) that can hit the United States and its leader, Kim Jong Un, has vowed to test-launch one at any time.
Experts and officials in the South and the United States believe Pyongyang is still some time away from mastering all the technology needed for an operational ICBM system, such as re-entry of the atmosphere and subsequent missile guidance.
Japan's Chief Cabinet Secretary Yoshihide Suga said the North's missile launch was "extremely problematic" and Tokyo has lodged a strong protest against its nuclear-armed neighbor.
South Korea's presidential Blue House called a National Security Council meeting to review the situation.
Topping the agenda of the U.S.-China summit in Florida will be whether Trump will make good on his threat to use crucial trade ties with China to pressure Beijing to do more to rein in Pyongyang.
A senior U.S. White House official said Trump wanted to work with China and described the discussions over North Korea as a test for the U.S.-Chinese relationship.
Trump wants China to do more to exert its economic influence over unpredictable Pyongyang to restrain its nuclear and missile programs, while Beijing has said it does not have that kind of influence.