President Bush says he expects North Korea to abide by international agreements it has made prohibiting the testing of long-range missiles.
Speaking after a summit with EU leaders in Vienna Wednesday, Mr. Bush said North Korea faces further isolation in the world if it decides to carry out a missile test.
He also said he is pleased China has spoken out against North Korea's reported missile test plans.
North Korea has maintained a self-imposed test ban since 1999. It tested a missile in 1998.
The reclusive communist state says it has the right to test and develop missiles, but has neither confirmed nor denied it is preparing for a test launch.
The United States Wednesday rejected an offer from a North Korean diplomat for direct talks with Pyongyang on the missile issue. U.S. officials say any dialogue with Pyongyang must come in the context of six-party nuclear disarmament talks.
The talks include both Koreas, Japan, China, Russia, and the United States.
The United States and other countries have reported that North Korea is preparing to test a long-range ballistic missile with a range capable of reaching U.S. soil. Washington and its allies have said any launch by Pyongyang would be considered a provocation.
Tensions in the region have been mounting since last year when North Korea announced it had developed nuclear weapons.
The six-party nuclear disarmament talks have been stalled since November. North Korea has refused to return to the talks until the United States lifts financial sanctions against Pyongyang.
Washington has said the sanctions are not linked to the nuclear talks.