UNITED NATIONS — Lakhdar Brahimi is resigning as the international point man on Syria, the UN chief announced Tuesday, marking a second failure by the United Nations and Arab League to end the country’s worsening civil war and highlighting the deep divisions among the parties and key countries on how to restore peace.

With Brahimi at his side, UN Secretary-General Ban Ki-Moon said the joint UN-Arab League envoy will step down on May 31 after nearly two years. Brahimi will be following in the footsteps of his longtime friend, former UN secretary-general Kofi Annan, who resigned from the same job in August 2012 after failing to broker a cease-fire as the country descended into civil war.

Ban, who has been outspoken in trying to end the Syrian conflict since it began in March 2011, blamed Syria’s opposition but especially the government, the divided UN Security Council which has been impotent, and feuding influential nations for failing to help Brahimi achieve a peace agreement.

“He has faced almost impossible odds, with a Syrian nation, Middle Eastern region and wider international community that have been hopelessly divided in their approaches to ending the conflict,” Ban said. “That his efforts have not received effective support from the United Nations body that is charged with upholding peace and security, and from countries with influence on the Syrian situation, is a failure of all of us.”

Brahimi managed to get officials from President Assad’s government and the opposition to two rounds of U.S. and Russian-brokered peace talks in Geneva aimed at establishing a transitional government, but they ended without an agreement. 

Diplomats said both sides sparred over responsibility for the bloodshed and Assad’s future.

The same day Brahimi announced his resignation, U.S. President Barack Obama and National Security Advisor Susan Rice met with Ahmad Jarba, the president of the Syrian Opposition Coalition, at the White House to reaffirm their support for Jarba and his allies.

During their meeting, Obama welcomed the opposition’s leadership, while encouraging “the Coalition to further its vision for an inclusive government that represents all of the people of Syria,” according to a readout of the meeting provided by the White House.

U.S. Secretary of State John Kerry said on Thursday he had seen raw data suggesting that Syria used chlorine in gas attacks against its own people, though he said the data had not yet been verified.

French Foreign Minister Laurent Fabius has said Syria may have used chemical weapons involving chlorine in 14 attacks in recent months.

“I have seen the raw data that suggests that there may have been, as France has suggested, a number of instances in which chlorine has been used in the conduct of war,” Kerry told reporters in London.

“If it has, and it could be proven, then that would be against the agreements of the chemical weapons treaty and against the weapons convention that Syria has signed up to.”

Kerry, who earlier met foreign ministers from European Union and Gulf Arab countries that are opposed to Assad, said the data had not been verified.

Kerry said: “Every possible avenue that is available will be pursued by one country or another. We are open to the idea of providing aid through any means that will get to people who need it and while a decision has not categorically made, we are open to anything.”

But he declined to say whether that would include arming the Syrian rebels.

On Thursday, a massive car bomb ripped through a crowded garage near a rebel-held border crossing between Syria and Turkey, killing at least 43 people in an area that has seen fierce fighting between rival rebel groups, an anti-government activist group said.

The attack came as the Syrian army have seized the momentum of the country’s 3-year-old civil war ahead of presidential elections scheduled for June 3.

The Britain-based Syrian Observatory for Human Rights said the blast killed 43 people and wounded more than 80. Injured Syrians taken to hospitals in Turkey and later died are among the 43 killed, said Rami Abdurrahman, the head of the Observatory. The group relies on a network of activists on the ground.

The Local Coordination Committees, another activist group, also reported the car bombing but said only that it killed and wounded “dozens of people.”

Car bombings have become common in Syria as the influence of Islamic extremist groups has risen, dampening the support of the U.S. and its European allies for the opposition seeking to oust Assad. Opposition activists have blamed al-Qaida-linked fighters, who are engaged in deadly fighting between rival rebel factions in Syria, although no group claimed responsibility for Thursday’s blast.

An amateur video posted online showed women, men and children at the scene of the blast near the Bab al-Salameh border crossing in the northern province of Aleppo. In another video posted online by activists, burned out cars are seen in the area near the crossing and the site of the attack, as people walk pass pools of blood, with clothes and other personal belongings scattered all around.

People cross the border at Bab al-Salameh on foot so the garage was filled with vehicles transporting people to or from the crossing.

Rebels fighting Assad captured the border crossing on the Syrian side in July 2012, opening a key transit point for people and supplies. But the area has seen an uptick in clashes and attacks between rebel groups fighting for control of the crossing in recent months.