The Joongang Ilbo newspaper says North Korea appears to have successfully carried out a test on long-range ballistic missile engines.

Quoting multiple diplomatic sources, the Seoul-based daily said Thursday that North Korea had conducted an engine combustion test for its ballistic missiles at a launching pad in North Hamgyeong Province last month. Such tests are often considered the last step before an actual flight test of missiles.

The daily said that U.S. intelligence agencies think that the size of the combustion trace and the amount of liquid fuel used suggest that the test is part of an experiment to develop the Taepodong-2 missile. According to U.S. intelligence officials, the missile, if developed, would have a range of up to six thousand kilometers.

Sources added that the engine test may have been aimed at seeking negotiating leverage at the next round of six-way nuclear talks set for later this month.