By Chris Buckley - Analysis

BEIJING (Reuters) - U.S. President Barack Obama will be seeking China's backing over North Korea and Iran when he visits this month, but Beijing appears increasingly assertive about what Western pressure it accepts or rejects.

Obama's summit in China in mid-November is sure to cover trouble-spots where Washington hopes Beijing will throw more of its growing political and economic weight behind efforts to defuse disputed nuclear programs or diplomatic standoffs.

China has bowed to such demands before, reluctantly backing limited U.N. sanctions against Pyongyang and Tehran, while resisting tougher steps it saw as unwarranted or a threat to bilateral ties.

Such diplomatic haggling, with China accepting some Western demands while protecting its bilateral ties with targeted states, will not change. But recent signs suggest China may now be more willing to stand its ground.

China's continued economic growth and rise in diplomatic stature during the global financial crisis, and uncertainty over policy in Washington, had emboldened Beijing, said Andrew Small, a fellow at the German Marshall Fund in Brussels, who has studied China's ties with the "rogue states."

"Several years ago, China's position was much more externally driven. Foreign pressure and U.S. lobbying was much more important," Small said of those ties.

"The U.S. is still a big factor, but they're finding they can be more assertive without putting relations with the U.S. in jeopardy."

Obama was likely to find bargaining for China's support over nuclear programs in North Korea and Iran more drawn out, said Shi Yinhong, a professor of international security at Renmin University in Beijing.

"China will become more self-confident about handling pressure from the U.S.," said Shi. "It will still cooperate, but there's less a sense that concessions on these issues define the bilateral relationship."

SHORING UP TIES

Beijing charted more of its own course most clearly with its communist neighbor, North Korea.

Last month, Premier Wen Jiabao courted its secretive top leader, Kim Jong-il, with a visit and President Hu Jintao hosted one of Kim's confidantes and invited Kim to visit.

China remains worried about North Korea's atomic weapons and wants to revive nuclear disarmament talks, said John Park, an expert on ties between the two countries at the United States Institute of Peace in Washington D.C.

But recently China has focused more on healing bruised ties with the North, driven by a belief that Pyongyang appears set on keeping its small nuclear arsenal for a long time, and that U.S. policy remains uncertain.

"I think the Chinese did an assessment and realized that the U.S. approach is ineffective, so they had to recalibrate policy toward North Korea," Park said.

The resulting "massive injection of political capital from China" may embolden North Korea, which held its second ever nuclear test in May, he added.

Obama may also appeal to Beijing for stronger backing to international efforts aimed at Iran's nuclear ambitions.

China has backed U.N. resolutions pressing Tehran to cooperate with international demands it open its nuclear activities to U.N. inspectors.

But Obama may find Beijing less willing to give ground, even if Iran rejects a proposal that would send its enriched uranium abroad for processing into nuclear fuel, reducing worries that Tehran could use the material for nuclear weapons activities.

Tehran says its nuclear facilities are for peaceful ends.

In a sign China remains intent on preserving energy and trade ties with Iran, Premier Wen Jiabao last month hosted the First Vice President of Iran, Mohammad Reza Rahimi, telling him that bilateral cooperation was a priority.

Iranian oil made up nearly 12 percent of China's crude imports last year.

China has increasingly come to believe Western-backed sanctions have made drawing Tehran into effective negotiations harder, said Jin Liangxiang, a researcher at the Shanghai Institute for International Studies who studies the Middle East.

"On Iran, the Chinese simply can hide behind the Russians who have made it clear that they won't support tougher sanctions," Bonnie Glaser, an expert on China at the Center for Strategic and International Studies, wrote in an email response to questions.

Even if Russia swings behind any new sanctions, China would go along only if it could insulate its stake in Iran, said Small.

"The bottom line is that in any one of these cases, China has never completely dropped anyone," he said of Iran, North Korea and other states facing Western pressure.

"Economic issues now dominate relations with Washington, so China feels a bit more leeway on the security and foreign policy issues."

(Editing by Nick Macfie)