China has returned to the attack on a controversial referendum in Taiwan, just two days before it is held jointly with presidential elections.
Opposition candidate Lien Chan campaigned in his northern stronghold
Foreign Ministry spokesman Kong Quan said the referendum was in effect a move towards independence and would damage regional stability.
Meanwhile a senior Taiwanese official said China had made a mistake by refusing to negotiate with the island.
The row coincided with a final campaign push by the two candidates.
President Chen Shui-bian met student leaders, as he tried to persuade young people to support him as many did when he swept to power in 2000.
He was also boosted by an endorsement from Lee Yuan-tseh, a respected Nobel prize-winning chemist who backed him in the last election but has recently been highly critical of the government.
Opposition Kuomintang (KMT) candidate Lien Chan visited his northern stronghold in Taipei county, where he was handed turnips - symbolising good luck - by supporters.
He also has several major rallies planned in the south of the island.
As well as electing a new leader, Taiwanese voters will be asked to vote in a referendum on defence spending and relations with China.
But Beijing fears that the referendum will set a precedent for a future vote on independence from China.
President Chen is looking to younger voters
"Some people in Taiwan, under the pretext of democracy, are organising a referendum that is in fact aiming for independence and damages the stability in the Taiwan Straits," spokesman Kong Quan told journalists.
Analysts say the news conference was Beijing's last scheduled opportunity to comment on the issue before Saturday's election.
But Tsai Ing-wen, head of Taiwan's Mainland Affairs Council, said a "sensible" leadership in China would have begun talks with the island.
"Over the last four years, China has probably made a major mistake in not engaging in talks with the people of Taiwan," she said.
"They have this feeling Taiwan is moving away from them. A sensible government in Beijing would think the best way to convince the Taiwan people and government and to bring them closer is through dialogue."