WASHINGTON — Japan’s new prime minister declared Friday he would make his country a stronger U.S. ally and joined President Barack Obama in warning North Korea that its recent nuclear provocations would not be tolerated.

After meeting Obama in the Oval Office, Prime Minister Shinzo Abe also sent a clear message to China: that while Japan does not want confrontation with Beijing, it won’t tolerate challenges to its sovereignty over islands disputed by the two Asian powers.

Those regional tensions served as the backdrop for Friday’s meetings that came just two months after Abe began his second stint as Japan’s prime minister following a convincing election victory.

Obama said he and Abe were united in their “determination to take strong actions" in response to North Korea’s nuclear test this month, which followed a successful long-range rocket launch last month. That has propelled the isolated, authoritarian state closer to having a weapon of mass destruction that could threaten the U.S.

Abe said he and Obama have agreed to push for tougher sanctions by the U.N. Security Council and spelled out why Pyongyang’s actions are cause for worry.