WASHINGTON (AFP) ― U.S. President Barack Obama pledged Wednesday a “steadfast” commitment to defend Japan, including preventing nuclear attacks on its ally in the wake of North Korea’s third nuclear test, the White House said.

In a telephone call, Obama and Japanese Prime Minister Shinzo Abe discussed steps to respond to the “highly provocative violation of North Korea’s international obligations, a White House statement said.

Pyongyang triggered international outrage on Tuesday by carrying out its latest nuclear detonation in defiance of U.N. Security Council resolutions.

U.S. and South Korean monitors said the underground nuclear test was much more powerful than North Korea’s previous tests in 2006 and 2009. Obama and Abe agreed to cooperate on tougher U.N. sanctions against North Korea.

The pair “pledged to work closely together to seek significant action at the United Nations Security Council and to cooperate on measures aimed at impeding North Korea’s nuclear and ballistic missile programs,” the White House said.

A Japanese Foreign Ministry official said separately the two leaders “agreed to work together for the prompt adoption of a new U.N. resolution on enhancing sanctions” on North Korea.

Obama also “reaffirmed that the United States remains steadfast in its defense commitments to Japan, including the extended deterrence offered by the U.S. nuclear umbrella,” according to the White House.

Abe is due in Washington for talks with Obama later this month.