China's Vice-Premier, Qian Qichen, has begun highly-sensitive talks with senior officials from the Bush administration in Washington.
The issue of US arms sales to Taiwan was high on the agenda when Mr Qian met Secretary of State Colin Powell ahead of talks with President Bush on Thursday.
In remarks before their meeting, both Mr Qian and Mr Powell acknowledged areas of disagreement, but said it was important to work together where possible.
The best approach in a relationship
such as ours is to have candid talks
Other thorny topics up for discussion are human rights in China and US plans for a missile defence shield, which Mr Qian has described as the most sensitive issue in relations with the US.
On Tuesday, a top Chinese official warned of a "very serious" setback in relations if the US went ahead with the sale to Taiwan of four destroyers equipped with highly-sophisticated radar which can be linked to the shield.
long as both sides can be visionary... I'm sure China-US relations will enjoy a healthy
and steady growth
Mr Qian has refused to rule out a pre-emptive attack on Taiwan if Mr Bush goes ahead with the
"It all depends on the circumstances," he told a news conference in New York earlier in the week.
Analysts expect Mr Qian's meeting with the president to further define what Mr Bush means when he says China is a "strategic competitor" rather than a potential "strategic partner".
The proposed US missile defence shield will give early warning of attacks
On Monday, the State Department confirmed that the new administration was dropping former President Clinton's so-called "three Nos" policy:
- No support for Taiwan independence.
- No recognition of a separate Taiwanese Government.
- No backing for Taiwanese membership of international organisations.
The move reflects strong support in Congress for Taiwan, especially among President Bush's Republican party.
The difficult atmosphere also appears to reflect the new administration's shift in priorities in its relations with the region as a whole.
Since taking office, President Bush has placed renewed emphasis on traditional allies such as Japan and South Korea.
Protests outside the State Department
Mr Qian had been due to meet Mr Bush on Monday - but his meeting was delayed after the president decided to receive Japanese Prime Minister Yoshiro Mori first.
The issue of human rights is also likely to be contentious, after the Bush administration's backing for a resolution critical of China at the United Nations Human Rights Commission in Geneva.
Mr Qian's visit comes amid controversy over an American-based academic who is being held in Beijing.
The US has urged China to free Gao Zhan, who was detained along with her husband and their five-year-old son at Beijing airport last month.
She has been kept in custody though her husband and son were eventually released.