U.S. President Barack Obama on Wednesday slammed Russia's "aggression" in Ukraine but offered to lift sanctions against Moscow if it threw its weight behind an unraveling peace deal with Kiev.

The outstretched hand to Moscow came a day after pro-Russian guerrillas brushed off Ukrainian President Petro Poroshenko's limited self-rule offer and announced plans to set up their own parliaments in self-organized November 2 polls.

A new U.N. mission on Monday officially takes charge of peacekeeping operations in the Central African Republic, tasked with ending ethnic and religious bloodshed and helping to bring political stability.

During a ceremony due to start at the airport of the capital Bangui at 3:00 pm (1400 GMT), the task force known as MINUSCA will pick up the baton from the African MISCA force, backed by French and European troops.

The World Food Program said on Tuesday that it provided food to a record 4.1 million people inside Syria last month.

The U.N. agency said it was able to reach more people because of a Security Council resolution adopted in July that authorized the movement of humanitarian aid to Syrians in rebel-held areas without government approval.

U.N. Security Council envoys said Wednesday they had little hope of a swift end to South Sudan's eight-month long conflict, despite threatening sanctions during meetings with the warring leaders.

"We did not hear much from them that gave us hope that there will be rapid agreement," in peace talks, British ambassador Mark Lyall Grant told reporters, describing discussions with leaders as "disappointing."

U.N. Security Council envoys warned South Sudan's warring leaders Tuesday they would face sanctions if a civil war that has pushed the young nation to the brink of famine does not stop.

"The council has made it very clear: that it is prepared to impose consequences if there continue to be spoilers, if there continue to be people carrying out gross violations of human rights," U.S. ambassador to the U.N. Samantha Power said after meeting with President Salva Kiir.

Rival forces in South Sudan's civil war should face sanctions and an arms embargo, Human Rights Watch said Friday, reporting "extraordinary acts of cruelty" it said amounted to war crimes.

Thousands of people have been killed and over 1.5 million have fled almost eight months of carnage in the world's youngest nation, where aid workers warn of famine within weeks if fighting continues.

The United States and major EU nations called Monday for more pressure to get a ceasefire between Hamas and Israel, the French presidency said, as a conflict that has killed more than 1,000 Palestinians rages on.

The leaders of the United States, Germany, France, Britain and Italy "agreed to redouble their efforts to obtain a ceasefire. Pressure must increase to get there," the French presidency said.

The United Nations has launched an internal investigation into allegations that its joint peacekeeping mission in the troubled Darfur region has been covering up crimes by Sudanese forces against civilians.

The United Nations-African Union peacekeeping force UNAMID, which was established in 2007, is tasked foremost with protecting civilians and securing humanitarian aid for Sudan's Darfur, where violence has left nearly 300,000 dead and two million displaced.

Russia urged U.N. Security Council members Monday to back a draft statement to bar crude oil sales by "terrorist groups" in Syria, including as the Islamic State of Iraq and the Levant

The text voices the council's concern at oil fields in Syria being seized by militants, and cites ISIL and al-Nusra Front.

The Security Council on Wednesday extended for another year the U.N. mission in Mali, calling on it to prioritize efforts to facilitate peace talks and expand its presence in the north.

The maximum level of peacekeepers will remain the same, at 11,200 soldiers and 1,440 police, as will the arrangement under which French soldiers in Mali can lend a hand in cases of serious and imminent danger.