The U.N.'s outgoing special envoy to Yemen said Monday the parties there had been "very close" to reaching a political agreement before the current violence and that the main sticking point had been who would lead the Arab world's poorest country.

Jamal Benomar also told reporters that a new targeted arms embargo could "inadvertently restrict the flow of much-needed commercial goods and humanitarian assistance" during the crisis.

Benomar spoke just after his final briefing to the U.N. Security Council behind closed doors. He is stepping down after sharp criticism from Saudi Arabia and allied Gulf countries after his peace efforts fell apart in the violence.

The envoy said "thousands" of people, many of them civilians, have been killed in the chaos of an Iran-backed rebel uprising and Saudi-led airstrikes that over the past month have sought to turn them back.

Benomar warned that the conflict is "becoming a confrontation with competing local and regional agendas" and that al-Qaida's most dangerous branch, based in Yemen, is benefiting from the instability.

And he said lasting peace in Yemen is possible only if Yemenis "determine their future free from interference and coercion from outside forces."

The envoy had been tasked in 2011 with finding a peaceful transition for the strategic Mideast country after the Arab Spring, and for a while the country had been praised as a model. Then the Shiite Houthi rebels last year swept through the country from the north, seized control of the capital and earlier this year caused the Western-backed president to flee the country.

Benomar did not get into many details of the talks that he said had been close to reaching a deal but said "substantial agreement had been reached on the core element of a power-sharing agreement." The problem had been the issue of the presidency, he said.

Those talks had been extensive. In the two months before the launch of the airstrikes, the U.N. had facilitated "around 65 plenary and working group meetings and more than 150 bilateral meetings with all sides," he said.

He would not blame any one party for the failure to reach peace.

"I told the Security Council that the collapse of the transition was not the fault of one side, but rather the result of accumulated mistakes and miscalculations made to varying degrees to all sides," he told reporters.

Early this year, he had warned the council of Yemen's possible collapse.

The current president of the U.N. Security Council, Jordanian Ambassador Dina Kawar, did not speak to Benomar's criticism of the council. She told reporters that recent council resolutions on Yemen, including one imposing an arms embargo on the leaders of the Shiite group, "have to be respected."