CAIRO -- While opponents to a constitutional referendum called by Egyptian President Mohammed Morsi have successfully mobilized protests that have drawn thousands to demonstrations at the presidential palace in the past week, they have yet to agree on how to approach next weekend’s vote, divided over whether to keep pushing for a delay, boycott or urge Egyptians to vote the proposed constitution down.

“We are still waiting to see the position of the revolutionary groups and the opposition so that we take a unified position. We won’t take a decision on our own,” said Mosaab Shahrour, a member of the April 6 movement, a leading opposition group.

That indecision could undercut what many say is the opposition’s best chance to hand Morsi and his Islamist supporters a defeat in a venue that Morsi would have to recognize as legitimate – unlike his battle with the country’s judges, who he says are dominated by appointees of the discredited regime of toppled President Hosni Mubarak.

Morsi made one concession on Saturday to his opposition, though it was unclear whether that would unify or divide his opponents.

After a meeting of 54 Morsi opponents and supporters held at the presidential palace, a Morsi adviser said the president had agreed to cancel his controversial Nov. 22 declaration in which he exempted his decisions from judicial oversight. He also agreed that if the constitution is defeated, he would call elections to select a new constitutional assembly.

But the adviser, Mohammed al Awa, said neither decision would halt the referendum, which now takes center stage as the key point in the three-week political standoff.

Opposition leaders didn’t immediately react to the announcement, which came after midnight. The prospect of being able to influence the selection of a new constitutional assembly could spur Morsi opponents to find a unified stand on the referendum. But Morsi’s refusal to delay it could prompt others to boycott the vote.

The inability on the part of liberals, secularists, Christians and moderates to present unified candidates and positions has been a major reason Islamists have dominated Egypt in the nearly two years since Mubarak resigned the presidency.

Last year, many of them sat out parliamentary elections in protest, allowing candidates of the Muslim Brotherhood and other Islamist conservative movements to dominate. During the presidential election earlier this year, the same group of opponents put up three candidates, dividing the vote and contributing to Morsi’s win in the runoff, in which his opponent was a former Mubarak official. During the writing of the constitution, Christian and secular members of the constitutional assembly withdrew, leaving members of the Muslim Brotherhood to dominate the group.

The meeting Saturday, which Morsi attended only briefly, offered another sign of the opposition’s divisions. The leading opposition groups refused to participate because Morsi had not delayed the referendum and had not canceled his Nov. 22 decree before the meeting was to take place.

That may change, with the decree now withdrawn. Still, opponents have not decided how best to confront the fact that the referendum will certainly take place. Opponents have called hundreds of thousands to the streets in nearly daily protests in the hopes of delaying the referendum. Now they say they hesitate to urge people to vote against the constitution in the referendum for fear of legitimizing the document, should it win approval.

“We don’t want to tell people to vote in the referendum because that means we accept what Morsi did by rushing the new constitution,” said one of Egypt’s most prolific liberal bloggers, an anonymous writer known only as “Big Pharaoh” who plans to vote no. “The majority did not write the constitution.”

Others, however, say it’s time for a new strategy, arguing that organizing voters to cast ‘no’ ballots is the only legitimate means they have to stop Morsi.

Election results from the first round of presidential voting last May suggest a concerted campaign to bring out ‘no’ votes could be successful. While Morsi won the most votes in that round – 25 percent – two liberal and secular candidates – Ahmed Shafik and Hamdeen Sabahi – won more votes combined – a total of 45 percent, with Shafik winning 23 percent and Sabahi, 22.

Without a unified message, the opposition will have a difficult time beating the organization of Morsi’s supporters, many of whom are members of the Muslim Brotherhood, Egypt’s best-organized group.

The Brotherhood is already urging voters to support the referendum, a campaign that began just hours after the constitutional assembly completed its draft.

Ismail is a McClatchy special correspondent.