U.S. President Barack Obama told the U.N. General Assembly Wednesday there can be “no shortcut” to end the Israeli-Palestinian conflict.

Mr. Obama said he is frustrated by delays in the peace process, but continues to believe the dispute must be solved through negotiations between the Israelis and Palestinians, and not at the United Nations. Palestinian leaders have said they will ask for admission to the U.N. as an independent state.

More broadly, Mr. Obama said it has been a year of “seismic” democratic change in the Arab world. He said in the aftermath of the so-called “Arab Spring,” U.N. members “have more work to do” to help nations rebuild.

Mr. Obama said the “unprecedented mandate” to intervene in Libya is an example of what international cooperation can achieve, and said efforts by the U.N. and Arab League prevented what could have been a “massacre” during the nation's political unrest earlier this year.

He called for sanctions on the Syrian regime, saying the Syrian people have shown dignity and courage in their pursuit of justice.

President Obama praised developments in South Sudan, where a successful referendum has resulted in self-determination for the new African nation. And he noted that efforts by the U.N. Security Council in Ivory Coast have helped move the country from political crisis to a democratically elected government.

Mr. Obama also singled out threats to global security, like nuclear weapons. He called for isolation and greater pressure on Iran and North Korea for misuse of their nuclear weapons programs.

As the General Assembly meeting opened Wednesday, U.N. Secretary-General Ban Ki-moon urged leaders to push for advances in the stalling Mideast peace process and to support nations transitioning to democracy in the Arab world.

During his opening remarks Mr. Ban pledged “unrelenting” efforts to move the peace process forward. He also called on leaders from the 193 member states to act now on climate change and to prevent conflict from erupting around the world.

Brazilian President Dilma Rousseff on Wednesday became the first woman in U.N. history to open the general debate portion of the assembly.

Rousseff the world is going through a difficult time and all members of the international community must cooperate to solve its problems. She also said she is confident that this will be the “century of women” and noted that in her native Portuguese language, the words “courage” and “sincerity” are of the feminine gender.

More than 30 other world leaders, including French President Nicolas Sarkozy, are addressing the assembly on Wednesday.

The Palestinian effort to secure statehood recognition by the U.N. Security Council has become the central focus of the week-long meeting. The United States and its key diplomatic partners are involved in intense diplomacy to block the Palestinian government's bid. President Mahmoud Abbas will submit the application for full U.N. membership to the Security Council on Friday.

President Obama was to meet separately Wednesday with Israeli Prime Minister Benjamin Netanyahu and Mr. Abbas.