President Barack Obama and the prime ministers of Australia and Japan are demanding justice for those who shot down a Malaysia Airlines jet over eastern Ukraine in July, killing 298 people.
Obama held a three-way meeting Sunday with Australia's Tony Abbott and Japan's Shinzo Abe during the Group of 20 economic summit in Brisbane, Australia.
Russian-backed rebels are suspected of firing the missile that brought down the plane.
The three leaders reaffirmed their opposition to Russia's annexation of the Crimean Peninsula and its action to destabilize eastern Ukraine. The Kremlin has denied having any troops and weapons in Ukraine, even after NATO and European monitors reported convoys of Russian tanks and arms crossing the border this past week.
Without mentioning China by name, the three leaders also called for the peaceful resolution of maritime disputes in accordance with the law. China is at odds with Vietnam, the Philippines and Malaysia over fishing and oil rights in the South China Sea and with Japan over a chain of uninhabited islands.
These governments and the United States accuse China of flaunting its military strength to intimidate its neighbors — allegations the Chinese deny.
The White House also said that the U.S. and Japan had pledged $4.3 billion to the Green Climate Fund to help developing nations deal with global warming.
The G-20 summit ends Sunday with a communique expected to say that the nations agree on a "comprehensive and coherent" plan to expand major economies by 2.1 percent.
Abbott had challenged G-20 members to come up with a definite plan to add $2 trillion to the world's gross domestic product in hopes of creating jobs and boosting free trade.
On Saturday, after joining leaders of the 20 major economies for lunch, Obama went to the University of Queensland to deliver a speech on foreign policy. He said the United States maintains its leadership role in the Asia-Pacific region and — as the world’s only superpower — has a unique responsibility that it gladly embraces. He mentioned Russia.
'Threat to the world'
"We're leading the international community in the fight to destroy the terrorist group ISIL, we're leading in dealing with Ebola in West Africa and in opposing Russia's aggression against Ukraine — which is a threat to the world, as we saw in the appalling shoot-down" of the Malaysian jetliner, Obama said.
Twenty-seven Australians were among those killed when Malaysia Airlines Flight 17 was shot down.
Russian state-run television aired photos Saturday showing what it said was proof that a Ukrainian fighter jet shot down the Malaysia Airlines jet. Ukrainian sources said the photos were forged.
Obama was not the only world leader who voiced criticism of reported Russian activities in Ukraine.
Before meeting with Russian President Vladimir Putin, British Prime Minister David Cameron warned that the West could impose more sanctions on Russia. German Chancellor Angela Merkel said events Ukraine were hindering efforts to grow the world economy. And Canadian Prime Minister Stephen Harper agreed to shake Putin's hand, but bluntly told him to "get out of Ukraine."
Also on Saturday, the G-20 issued a statement on Ebola, committing to do what is necessary to "extinguish the outbreak." The group called on governments that have not yet done so to make financial contributions to fighting the disease.
Some information for this report was provided by VOA's Luis Ramirez in Brisbane.