China and the United States suffer a trust deficit that Vice President Xi Jinping's trip to Washington could help ease, a Chinese diplomat said in a speech published on Tuesday, playing down Chinese fears about a U.S. pivot towards Asia.

China's president-in-waiting, Xi, will visit the United States starting next Tuesday, going to the farming state of Iowa where he stayed briefly in 1985 and to Los Angeles, the Chinese Foreign Ministry said, confirming an earlier statement from the White House.

The speech by China's Vice Foreign Minister Cui Tiankai was the latest sign that Beijing wants Xi's visit to keep to an upbeat tone, despite frictions that trouble relations, most recently over its decision to veto a U.N. Security Council resolution on the increasingly bloody conflict in Syria.

But Cui said mutual misgivings have clouded relations between the world's two biggest economies, despite deep trade ties and greater foreign policy dialogue.

There is certainly a trust deficit between China and the United States, Cui said in the speech in Shanghai on Monday that was posted on the Chinese Foreign Ministry's website (www.mfa.gov.cn).

Each time the Sino-U.S. relationship hits problems, there are voices that fundamentally doubt the relationship. There are constantly those who want to overturn this relationship that can truly be called too big to fail, said Cui, whose portfolio includes overseeing ties with the United States.

Therefore, nurturing and deepening mutual trust remains a major issue that both sides must give full attention to and seriously address, he added.

Xi's visit to the United States, including a meeting with President Barack Obama at the White House on Tuesday, appears unlikely to bring big advances on Syria, Iran and other sources of friction, including human rights and trade imbalances.

Xi will also visit Turkey and Ireland after the United States, Chinese Foreign Ministry spokesman Liu Weimin told a daily briefing. He did not give specific dates for each stop.

While Liu would not say what specific topics would be on the agenda, he did express unhappiness with Obama's recent announcement to create an enforcement unit to crack down on unfair trade practices in China and other countries.

Exerting pressure unilaterally is irresponsible behaviour and not conducive to resolving problems, Liu said.

For Xi, the U.S. visit will be a major step in signalling his readiness to take over as China's next top leader. His growing prominence indicates he is virtually certain to replace Hu Jintao as Communist Party chief late this year and then as state president in early 2013.

Xi could help counter some of the distrust, Cui suggested.

We hope that both sides will seize on this visit as an opportunity to enhance communication, expand cooperation and deepen friendship, said Cui.

He did not mention Syria nor did he directly mention the Obama administration's pivot to bolster the U.S. economic and military presence in Asia, which some critics in China have called a strategy to fence in their country.

But Cui stressed that China did not see conflict over regional influence as inevitable.

The Asia-Pacific is big enough to accommodate both China and the United States, he said. There's great potential for cooperation, and the key lies in mustering enough political will.

(Additional reporting by Ben Blanchard)