Nasser al-Kidwa, the deputy of international mediator Lakhdar Brahimi, has been removed from the small team running the Geneva peace talks that aim to end the war in Syria, diplomatic sources said on Monday.
"He has been sacked," one of the diplomats said. A member of Brahimi's team declined to comment.
Al-Kidwa, a former foreign minister of the Palestinian authority and nephew of Yasser Arafat, was appointed as a deputy to Brahimi's predecessor Kofi Annan in March 2012, and continued in the role under Brahimi.
Earlier, the UN humanitarian chief said a meeting of key international players involved in trying to end the Syrian conflict endorsed a dozen steps to ensure immediate humanitarian relief.
Valerie Amos didn't detail the actions, saying only that they involved "access to besieged communities, access to hard to reach areas, demilitarization of schools and hospitals" and progress on funding.
Amos spoke after a daylong meeting Monday in Rome hosted by Italian Foreign Minister Emma Bonino tried to make progress on the humanitarian crisis after Syrian peace talks in Geneva last week failed to produce a plan.
At the start of the meeting, Bonino said the Syrian crisis "is the biggest humanitarian tragedy of our time" in terms of the number of people killed or displaced.
Bonino said "the international community has largely failed" in ensuring adequate access to humanitarian aid in Syria.
"The shame falls on us. On all of us. Some more than others, evidently," Bonino said in her speech at the third meeting of the High Level Group on Humanitarian Challenges in Syria, being held in Rome.
"We meet today because, despite our joint efforts, and despite the tremendous work being done by the UN special envoy to Syria Lakhdar Brahimi, things are not moving forward," Bonino told delegates.
"We have to join forces to convince countries and authorities that are still resisting," she urged.
Bonino bemoaned the fact that a lot of aid has reached the region, but is being held up, often at the border with
Syria, and all it needs is "a green light, a go."
"That is what makes this, I think, a real shame," she added.
More than 130-thousand people have died since the uprising against Syrian President Bashar Assad began in March 2011, and millions of people have been uprooted from their homes.
At least 2.3 (m) million people have fled Syria, most of them to neighboring countries.
On the field:
Syrian activists said government airstrikes on rebel-held neighborhoods in the northern city of Aleppo have killed at least 18 people, including five children.
The Britain-based Syrian Observatory for Human Rights says Monday's air raids hit the districts of Hanano, Qadi Askar and Mouwasalat.
The attacks come a day after President Bashar Assad's air force killed at least 36 people in opposition areas of Aleppo.
Syrian military aircraft have been pounding rebel areas of the divided city for weeks. Many of the air raids have been carried out by helicopters that drop so-called barrel bombs primitive contraptions packed with explosives, fuel and scraps of metal that cause severe damage on impact.
REUTERS/AP