An Obama meeting with the Dalai Lama would "seriously undermine the political foundation of Sino-U.S. relations," said Zhu Weiqun, executive deputy head of the Communist Party's United Front Work Department in charge of recent talks with the exiled Tibetan leader's envoys.
Zhu was speaking at a news conference where he said no progress had been made at the talks with envoys of the Dalai Lama on changes to the Himalayan region's status.
The warning to Obama comes after signals from U.S. officials in recent weeks that Obama might soon meet the exiled Tibetan leader - something Chinese officials are keen to avoid before President Hu Jintao travels to Washington, possibly in April.
Zhu said any arguments that the Dalai Lama was just a religious figure were wrong, calling the 1989 Nobel Peace Prize laureate the "head of a separatist group."
No date for Obama's meeting with the Dalai Lama has been announced, but White House spokesman Mike Hammer said last month that "the President has made clear to the Chinese government that we intend to meet with the Dalai Lama, it has been his every intention."
Bilateral relations have already been strained by the U.S. announcement Friday that it planned to sell.
Beijing quickly suspended military exchanges with Washington and announced an unprecedented threat of sanctions against the U.S. companies involved in the sale.
Zhu did not give any details on what China would do if Obama meets the Dalai Lama. "We will take corresponding measures to make the relevant countries realize their mistakes."
Representatives of the United Front meet over the weekend with two Tibetan envoys for their first talks in 15 months, but Zhu said China would discuss only the future of the exiled spiritual leader, not any greater autonomy for Tibet.
"There is no room for negotiation or concession on the part of the central government on these issues," Zhu said.
China maintains that Tibet has been part of its territory for centuries, but many Tibetans say the region was functionally independent for much of its history.
At the last talks in 2008, the Dalai Lama's envoys proposed a way for Tibetans to achieve more autonomy under the Chinese constitution - a key demand of the minority community. But China apparently rejected the plan, saying it would not allow Tibet the kind of latitude granted to the territories of Hong Kong and Macau. Chinese officials said they were only willing to discuss the return of the Dalai Lama, who fled to exile in 1959.
The Tibetan government-in-exile in Dharmsala, India, said last week it hoped the two sides would be able to revisit the proposal for greater autonomy.
Beijing demonizes the Dalai Lama and says he seeks to destroy China's sovereignty by pushing independence for Tibet. The Dalai Lama has maintained for decades he wants some form of autonomy that would allow Tibetans to freely practice their culture, language and religion under China's rule, not independence.
Tibetan areas have been tense in recent years, with the minority community complaining about restrictions on Buddhism, government propaganda campaigns against their revered Dalai Lama, and an influx of Chinese migrants that leave Tibetans feeling marginalized. Those feelings boiled over in deadly anti-Chinese riots in 2008 that shocked Beijing's leaders.