Australia has again failed to secure an invitation to a meeting of the International Syria Support Group (ISSG) that is trying to find a political solution to the conflict.

Australian remains out despite its lobbying effort after Russia blocked its attendance at an earlier meeting.

The ISSG convenes in New York on Friday with more than 20 participating countries and organisations including the Organisation of Islamic Co-operation (OIC). The OIC is expected to be the only addition since the November gathering in Vienna.

After the US, Australia has the second-largest military commitment to the fight against Islamic State.

Although it is not entirely clear why Australia could not make its way into this week’s meeting, Australian officials believe Russia and possibly some other countries remain against expanding the size of the conference, apart from adding the OIC.

Attendance is limited to permanent members of the UN Security Council, and various European and Middle Eastern countries. Some 14 of the 23 countries making military contributions were not at the last meeting.

The talks are set to follow up on the two earlier sessions of the group, reviewing progress towards negotiations between the Syrian government and opposition, as well as towards a nationwide ceasefire.

Also, participants are expected to discuss a meeting earlier this month hosted by Saudi Arabia to bring together opposition groups, ahead of their negotiations with the Syrian regime.

There is work as well on getting agreement on determining who are terrorist groups and individuals.

The New York discussion is expected to be followed by a UN Security Council meeting and a resolution on the process. This resolution would codify a framework agreement drafted at the November meeting.

The Russians were not keen on the New York meeting being held now but came round in talks in Moscow this week, when US Secretary of State John Kerry met Russian President Vladimir Putin and Foreign Minister Sergei Lavrov.

While the US and Russia are sponsoring the effort to get a political solution, differences over various issues, including the fate of Syrian President Bashar al-Assad, have made negotiations very difficult.

Moscow also reacted badly to the talks in Saudi Arabia, saying that several “terrorist” groups had taken part in them.