US Secretary of State John Kerry left Wednesday for a whirlwind day of diplomacy focused on the conflict in Syria and efforts to resolve the crisis in Ukraine.

The top US diplomat was also to meet in London with Palestinian Authority President Mahmoud Abbas for the first time since peace talks with the Israelis collapsed last month.

The focus of his trip though will be a meeting on Thursday of the core group of supporters of the Syrian opposition, and it comes just after UN-Arab League peace envoy Lakhdar Brahimi stepped down after almost two years of fruitless efforts to end the war.

“Mr. Brahimi did not fail,” Kerry insisted late Tuesday, blaming Syrian President Bashar Assad “who will not negotiate, who absolutely refused to negotiate at every single session.”

“This represents a continuation of the stubborn clinging to power of a man who is willing to drop barrel bombs on his people, to gas them, to shell artillery on innocent civilians, to starve people in their homes, and somehow claim a right to be able to run a country,” Kerry added.

Kerry will meet with ministers from Britain, Egypt, France, Germany, Italy, Jordan, Qatar, Saudi Arabia, Turkey and the United Arab Emirates, for their first ministerial talks on the conflict since January.

Syrian opposition leader Ahmad Jarba is also to attend after spending more than a week having high-level meetings in Washington in a bid to strengthen US support for the rebels in their battle against Assad.

Specifically he pleaded for anti-aircraft missiles to shoot down regime aircraft which are unleashing deadly barrel bombs on Syrian civilians.

The talks would focus on “the international community’s efforts to ease humanitarian suffering inside Syria, to bolster support for the moderate transition” and advance moves for a political transition, a senior US administration official said.

“The US understands the urgency of the crisis in Syria and stands firmly on the side of the Syrian people,” the official said, asking not to be named.

The ministers would discuss how to “change the realities on the ground in order to raise the prospects that the regime will participate in meaningful political dialogue.”

Kerry will also meet with his European counterparts to discuss ways to support the upcoming presidential elections in Ukraine, amid moves to try to draw up tougher sanctions against Russia, accused of trying to destabilize the country.

The US diplomat will “discuss the importance of remaining in lockstep and being prepared to put in place consequences if those are warranted,” another US official said.