U.S. Secretary of State John Kerry has warned Moscow to halt its bombing of Syrian rebel groups, after UN-mediated peace talks between Damascus and the opposition broke down in Geneva.
Kerry told his Russian counterpart, Sergei Lavrov, in a phone conversation on February 4 that an existing UN Security Council resolution already called for an immediate cease-fire in Syria in order to allow humanitarian aid through to besieged cities.
Kerry, speaking at a donors conference on Syria in London, also said he and Lavrov had agreed the need to discuss how to implement a cease-fire.
"I had a conversation this morning with Foreign Minister Lavrov. We discussed, and he agreed that we need to discuss, how to implement the cease-fire and also how to get [humanitarian] access by both parties," Kerry told reporters.
World leaders are meeting in London to raise $9 billion for those affected by the nearly five-year-old Syrian conflict.
Around 70 leaders are attending the February 4 conference, which aims to agree plans for economic and humanitarian aid to assist 4.6 million Syrian refugees living in neighboring countries.
German Chancellor Angela Merkel pledged to spend $2.6 billion by 2018 to aid Syrian refugees as the international meeting got under way.
Britain has pledged around $1.75 billion in new aid by 2020, and U.S. Secretary of State John Kerry is due to announce a big U.S. commitment.
On February 1, international charity Oxfam criticized many countries involved in Syria, including Russia, for not helping the victims of the conflict, which has killed at least 250,000 people and forced millions to flee the country.