Speaking at the close of a meeting with Southeast Asian leaders in California, Obama pressed for a "halt to reclamation, new construction and militarization" of Asia's oceans, an indirect reference to China's rapid construction in the South China Sea of air strips and ports that could have military uses.
Obama said the U.S. "will continue to fly, sail and operate wherever international law allows" and added that "we'll support the right of our allies to do the same."
The two-day meeting between the President and ASEAN, or the Association of Southeast Asian Nations, was the first on U.S. soil and meant to foster closer ties as Washington looks for ways to counter an increasingly assertive Beijing. It was also meant to cement a pillar of Obama's foreign policy agenda in "rebalancing" resources and attention to the Asia Pacific.
Obama said he and leaders of the 10-member ASEAN group were also "reaffirming our strong commitment to an international order" with rules and norms that are universally observed and "in which the rights of all nations, large and small, are observed."
Obama stressed the need for freedom of commerce, adding that "any disputes must be resolved peacefully."
But as has often happened in the last few years, the administration's desire to focus on East Asia has been disrupted by the Middle East, and at Tuesday's news conference reporters quizzed Obama on whether he has been "outfoxed" in Syria by Russian President Vladimir Putin and whether he would pursue ISIS as it expands in Libya.
On Libya, Obama said the U.S. "will go after ISIS wherever it appears, the same way we go after al Qaeda wherever it appears."
He made clear that the U.S. would continue to target ISIS leaders in particular.
"We will continue to take actions where we got a clear operation and a clear target in mind," Obama said, "and we are working with our other coalition partners to make sure that as we see opportunities to prevent ISIS from digging into Libya, we take them."
The President said that the conflict in Syria "is not a contest between me and Putin."
And Obama defended his assertion that in propping up Syrian President Bashar al-Assad, Russia is getting itself stuck in a quagmire and questioned the benefits of the Russian intervention, which has stabilized Assad's regime and helped his army make gains in northern Syria in recent weeks.
He argued that if Putin decides to stay in Syria, it could harm his country: "That's going to be pretty costly. That's going to be a big piece of business. And if you look at the state of the Russian economy, that's probably not the best thing for Russia."
Obama questioned whether there's "anyone who thinks somehow the fighting ends because Russia and the regime have made some initial advances" and pointed out that "about three-quarters of the country is under the control of folks other than Assad."
If Russia continues its "indiscriminate bombing," a nascent cessation of hostilities
forged in Munich last week likely won't work out, Obama said.
"What would be smarter would be for Russia to work with the United States" on some sort of political transition, Obama added. "We will see what happens over the next couple of days and we will continue to work with our partners who are focused on defeating ISIS."