Britain’s Foreign Secretary William Hague has pledged greater support for Syria’s rebel fighters, as the battle for the country’s commercial capital Aleppo intensified.

“Given the scale of death and suffering and the failure so far of the diplomatic process we will, over the coming weeks, increase our practical but non-lethal support,” Hague told BBC radio.

“We have helped them with communications and matters of that kind, and we will help them more,” he added. “It will not involve sending armaments.”

Hague expressed dismay at the former United Nations secretary-general Kofi Annan’s resignation as international peace envoy to Syria, describing it as “a bleak moment, not only for the country’s people but for our diplomatic efforts”.

Annan has said he quit because his plan to end the 17-month bloodshed never received the support it deserved.

Russia and China have jointly blocked three UN Security Council resolutions that would have imposed sanctions on the government of Syrian President Bashar al-Assad, and have refused to join international calls for his departure.

Hague insisted that the diplomatic process to end the violence was not dead, but he admitted: “Diplomacy has so far failed the people of Syria.

“We don’t give up on the diplomacy with Russia and China,” he added. “We will keep going with that as long as the situation continues, but we will have to do other things as well.”

Britain has joined the United States in condemning Russia’s opposition to UN action on the spiralling violence in Syria, where human rights monitors say 20,000 people have been killed.

British Prime Minister David Cameron held talks on Syria with Russian President Vladimir Putin yesterday, but the pair failed to hide their differences.

“There have been some differences in the positions that we’ve taken over the Syrian conflict,” Cameron told reporters.

“We both want to see an end to that conflict and a stable Syria, and will continue to discuss with our foreign ministers how we can take this forward,” he added.