Egyptian President Mohamed Morsi is urging opposition groups to join him in a dialogue about the country's future after he signed into law a new constitution that those groups bitterly oppose.

In a televised address late Wednesday, Mr. Morsi said the government and the opposition must cooperate to enable Egypt to solve what he called its “huge” economic problems.

In a conciliatory gesture, Mr. Morsi said he takes responsibility for “mistakes” made by his six-month-old government in trying to expedite a transition to democracy. Liberal groups criticized the Islamist president for unilaterally boosting his powers last month to ensure that a panel of fellow Islamists could finish drafting the constitution and submit it to a popular referendum without being challenged by the judiciary.

Egypt's electoral commission announced the results of the referendum Tuesday, confirming that the basic law was approved by 64 percent of voters in a two-stage vote earlier this month. Mr. Morsi signed the document into law hours later.

Only one-third of the electorate showed up to vote on the constitution, leading critics to question its legitimacy. Liberal opposition figure Mohammed ElBaradei also posted a tweet on Wednesday, saying the constitution is “void” because, in his view, it conflicts with international norms on freedom of belief and expression.

In his address, Mr. Morsi said the constitution protects the rights of citizens and treats them equally. But, he acknowledged that a “large segment” of the public disagrees, and said it is healthy for society to debate the issue.

Earlier in the day, Egypt's upper house of parliament, or Shura Council, met to swear in 90 new members appointed by Mr. Morsi and begin its constitutional role of passing legislation until a new lower house is elected in two months. The Shura Council is dominated by Islamist supporters of Mr. Morsi.

Egypt's lower house typically takes the lead on legislation but it was disbanded earlier this year by the military rulers who preceded Mr. Morsi. Opposition groups hope to win enough seats in coming lower house elections to effectively fight the new constitution in parliament.

Mr. Morsi is under pressure to secure broad domestic support for tax increases and other austerity measures demanded by the International Monetary Fund in return for a $4.8 billion loan to keep the economy afloat. The political crisis over the constitution has shaken public confidence, leading many Egyptians to buy dollars and withdraw their bank savings in recent days.

Mr. Morsi's government responded to those concerns on Tuesday, imposing a ban on people leaving or entering Egypt with more than $10,000 in cash. The move was seen as an attempt to conserve the country's dwindling foreign exchange reserves.