China would welcome assurance about the security of its financial assets in the United States, a senior diplomat said on Wednesday ahead of President Hu Jintao's visit next week, while playing down rifts between the two powers.

Chinese Vice Foreign Minister Cui Tiankai said North Korea and other issues that need cooperation between two global giants would come up during Hu's January 18-21 trip. Hu will have a summit with President Barack Obama on January 19.

While Obama may press Hu on China's yuan currency controls, Cui said Beijing had its own concerns about its big holdings of U.S. treasury debt.

China has amassed the world's biggest stockpile of foreign exchange reserves at $2.85 trillion, an estimated two-thirds of which is invested in U.S. assets.

Regarding the security of China's assets in the United States, if the U.S. side can offer a positive statement on that then of course we'd welcome that, and it's an issue we're paying attention to, Cui told reporters.

China regularly seeks assurances on the security of its U.S. investments before any formal high-level meetings with the United States.

Indeed, for two years running, Chinese Premier Wen Jiabao has used the most important press conference of the year during the annual parliament to say he is worried about the safety of China's investments in the United States.

The politically sensitive trade gap between the world's two biggest economies widened by 26 percent in 2010 to $181 billion in China's favor, Chinese data showed this week.

The growing gap provides fodder for critics of Beijing's tightly controlled currency regime who claim China keeps the yuan cheap to give its exporters an unfair advantage.

The briefing on Hu's trip, which touched on a series of sensitive economic and defense issues for the two countries, came as U.S. Secretary of Defense Robert Gates was wrapping up a visit in China intended to defuse military tensions.

Cui said differences in national conditions and development levels meant China and the United States could not avoid differing views and friction.

This is normal, he said. If we had no dealings with each other, then there would also be no friction.

But Cui said China shares broad common interests and goals with the United States on Korean peninsula issues, and repeated calls to restart six-party nuclear talks.

On Tuesday, Gates said North Korea could have inter-continental ballistic missiles within five years, and that the country posed a direct threat to the United States.

Obama is likely to urge Hu to increase pressure on North Korea, which triggered regional alarm by shelling a South Korean island and by claiming progress in uranium enrichment, which could give it a second pathway to making nuclear weapons.

China also conducted its first test flight of a stealth fighter jet on Tuesday, a move China said was not connected to Gates's visit.

I think China's rise in national power and China's expansion of international influence is an objective fact, Cui said, but added this could promote relations with the U.S. and other countries.

No other country has reason to feel worried or troubled about this. What you've raised (about the stealth fighter) had nothing to do with Defense Secretary Gates's visit or with China-U.S. relations, he said.