The Chinese prime minister has again warned Taiwan not to use democratic aspirations as a cover for separatism.
Wen will also seek to defuse disagreements over trade
Wen Jiabao was speaking after talks with UN Secretary General Kofi Annan at the start of a visit to the US.
Mr Wen, who is due to see President Bush on Tuesday, wants an unequivocal statement from the US of its opposition to Taiwanese independence.
The trip comes at an awkward time in Sino-US relations, with not only Taiwan but trade and North Korea key issues.
The BBC's Adam Brookes in Washington says the recent pronouncements of the Taiwanese President Chen Shui-bian have rattled both Beijing and Washington.
President Chen says he is going to hold a referendum in March to ask the Taiwanese people whether or not they feel threatened by China's military posture.
Beijing sees such a referendum as provocative while Washington worries that Mr Chen is undermining the security status quo in order to gain votes.
Asked about the referendum plans by reporters in New York, Mr Wen said China understood "the aspiration of the people in Taiwan for democracy".
"The essence of the problem now is that the separatist forces within the Taiwan authorities attempt to use democracy only as a cover to split Taiwan away from China and this is what we will never tolerate," Mr Wen was quoted as saying by Reuters news agency.
But he added that as long "as there is still a glimmer of hope, the Chinese Government will not give up its efforts for a peaceful unification and a peaceful settlement."
Beijing has derived some comfort from the fact that Taiwan's opposition-dominated legislature succeeded in watering down the referendum bill before it was passed 10 days ago.
However, Taiwan's cabinet said on Monday that it would try and repeal some of the bill's watered-down clauses.
Mr Annan stressed that all differences between China and Taiwan had to be resolved politically.
"We maintain the One China Policy and the need to resolve all issues peacefully," he said.
Another important topic for Mr Wen's discussion with the Bush administration will be North Korea.
Our correspondent says that the Bush administration feels that it does not need another regional crisis on its hands, whether in the Taiwan Strait or in North Korea, and it will be looking to secure China's co-operation in avoiding both.
When it comes to trade, Mr Wen will want to defuse tensions over a widening dispute.
The US is facing a $120bn trade deficit with China this year and it has announced plans to limit imports of some Chinese goods which it says were dumped.
Beijing also wants Washington to lift export curbs on high tech items.
China still has some leverage with the US, particularly given its crucial role in putting pressure on North Korea to attend six party peace talks.
But with so many tricky issues on the table, this trip will set the tone for Sino-US ties and it is likely to prove the most difficult diplomatic challenge yet for Mr Wen.