Wu asked Chen and the CEC to give a positive answer by noon today.
Otherwise, Wu threatened, the Kuomintang, which sponsors one of the referendums, would start calling on voters to boycott both votes.
"We will issue a declaration when no positive answers come before the deadline," Wu said. He will preside over a central standing committee meeting on the U.N. bid this morning.
He refused to disclose how the declaration would be worded, but the indications are that the Kuomintang would ask voters not to receive ballots for both referendums.
The other referendum, sponsored by the ruling Democratic Progressive Party, asks the electorate to vote on the accession to the United Nations under the name Taiwan. The Kuomintang wants a return of the Republic of China to that world body, from which it was ousted in 1971.
Lawmakers of the opposition party, who form a three-fourths majority in the Legislative Yuan, are ready to adopt on Friday a resolution urging the government to redouble efforts to make Taiwan a U.N. member again.
In a warmup for the resolution, which is intended to force the CEC to call the referendums and the presidential election separately, Kuomintang legislators questioned Premier Chang Chun-hsiung if he could order the delinking of one from the other.
"It's up to the Central Election Commission," the premier replied.
Asked the same question at a Legislative Yuan committee meeting, CEC chairman Chang Cheng-hsiung said he couldn't.
The decision to hold them together was a collective one, Chang said. It takes CEC commissioners to decide to reconsider the previous decision, he added.
"I'm asking commissioners whether they would reconsider," Chang told Kuomintang lawmakers. Apparently, time is running short for the CEC to call a plenary meeting to make another collective decision making it possible for voters to cast ballots for president and vice president alone.
As regards the Kuomintang resolution, Chang said, "It's not binding on the Central Election Commission to cancel the March 22 referendums."
"Even if the resolution is passed," Chang pointed out, "the referendums will be held as scheduled."
Ma Ying-jeou, Kuomintang candidate for president, said he would abide by any decision his party takes today. He did so in the run-up to the legislative elections-cum-referendums on last Jan. 12.
More than half of eligible voters refused to receive ballots or stayed away from the polls to kill the referendums on recovery of ill-gotten Kuomintang assets and prosecution of corrupt top government officials, including President Chen.
To be valid, a referendum has to be voted on by at least half of the electorate; a simple majority passes it.
Frank Hsieh, Ma's DPP rival, urged voters to vote for both U.N. bid referendums.