By Jeff Mason

RANCHO MIRAGE, Calif. (Reuters) - President Barack Obama gathered with leaders from Southeast Asia on Monday to strengthen trade ties and form a common stance over the South China Sea in a summit that the White House hopes will solidify U.S. influence in the region.

Obama, who leaves office next year, has championed a foreign policy pivot to Asia during his presidency and is determined to present the United States as a Pacific power.

His meeting with leaders from the Association of Southeast Asian Nations (ASEAN) was aimed at cementing that legacy.

"This reflects my personal commitment, and the national commitment of the United States, to a strong and enduring partnership with your 10 nations," he said at the start of the two-day summit at Sunnylands, a California resort.

The meeting, at the same location where Obama once hosted Chinese President Xi Jinping, was designed to demonstrate Washington's role as a counterweight to Beijing and as an eager trading partner with ASEAN members.

White House National Security Adviser Susan Rice told reporters U.S. companies had more than doubled investment in the region since 2008.

On Monday the leaders were slated to focus on economic issues, including discussion of the Trans-Pacific Partnership deal, which includes four ASEAN members: Vietnam, Singapore, Brunei and Malaysia. Others are interested in joining, and the White House wants to make sure the pact takes effect.

On Tuesday, the leaders will discuss maritime issues, particularly the South China Sea, where China and several Southeast Asian states have conflicting and overlapping claims.

White House officials have said Obama would deliver a tough message to China that disputes over the South China Sea must be resolved peacefully and not by bullying.

"Here at this summit, we can advance our shared vision of a regional order where international rules and norms, including freedom of navigation, are upheld and where disputes are resolved through peaceful, legal means," Obama said.

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The challenge may be to get all ASEAN countries to agree on a strong statement on the issue. Officials say China has put pressure on countries such as Cambodia and Laos not to sign.

"I'm ... confident that our shared commitment to upholding these norms will be reinforced," Rice said.

China's role in the region hung over the meeting. Rice said she expected China would support new international sanctions on North Korea for its recent rocket launches.

An editorial in the influential Chinese tabloid the Global Times on Tuesday said the summit was the wrong place to discuss South China Sea issues and that it would not yield "striking geopolitical decisions".

"ASEAN countries have no such desire, and the U.S. knows it is not able to do so," the Global Times said, repeating Beijing's stance that disputes in the sea should be handled bilaterally.

Advocacy group Human Rights Watch urged the Obama administration to object to human rights violations in countries such as Cambodia and Thailand during the summit. The president touched on the issue without specifics during his remarks.

"Here at the summit, we can reaffirm that strong, prosperous and inclusive societies require good governance, rule of law, accountable institutions, vibrant civil societies and upholding human rights," he said.

Combating climate change and cooperating on counter-terrorism and the fight against Islamic State militants were also on the agenda.

Obama returns to Washington on Tuesday.





(Additional reporting by Roberta Rampton, Bruce Wallace and David Brunnstrom, and Michael Martina in BEIJING; Editing by Dan Grebler and Simon Cameron-Moore)