World leaders are close to agreeing on a statement on the conflict in Syria despite deep divisions between Russian President Vladimir Putin and the rest of the G8, officials said on Tuesday.

The leaders of the Group of Eight most industrialised nations are still working out the exact wording of the communique that they will issue at the end of the two-day summit in Northern Ireland, officials from two Western nations told AFP.

The statement is likely to focus on less contentious issues such as the need to push for a peace conference in Geneva and on humanitarian aid, one official said on condition of anonymity.

Syria was discussed for a second time on Tuesday during a session on counter-terrorism, following a lengthy discussion during the leaders' dinner on Monday, another source said.

British Prime Minister David Cameron had drawn up a list of five areas that he thought there could be agreement on with Putin at the dinner.

An official said there were "very frank" discussions at the dinner, especially on the issue of chemical weapons.

The United States, Britain and France say President Bashar al-Assad's forces have used nerve gas but the regime's ally Russia says there is no evidence to support their claims.

However there was agreement on the need for a transitional authority that would include all communities in Syria, which is increasingly divided along sectarian lines after more than two years of conflict.

Issues such as arms -- after Washington said last week it would start supplying weapons to the rebels -- were largely left off the table, officials said, adding that negotiating teams had been instructed to work through the night to agree on a statement.