BRISBANE, Australia (AP) — Closing out his Asia-Pacific tour, President Barack Obama called on Asia-Pacific nations to join the U.S. in confronting big global challenges, from climate change and poverty to violent extremism.

Speaking to university students in Australia, Obama insisted that skeptics who discount his efforts to strengthen U.S. engagement in the region are overlooking his successes and underestimating opportunities that remain in his final two years in office.

Obama's speech formed the capstone of a weeklong trip to China, Myanmar and Australia, where he sought to reinvigorate ties to a region he's made central to his foreign policy.

Leaders in Asia question whether that effort has been more talk than action. But Obama says the U.S. is working every day to make American power a positive presence in the region.