The United Nations said on Tuesday it was seeking to re-settle more than 450,000 Syrian refugees, some one-tenth of those now in neighbouring countries, by the end of 2018, but conceded that it was battling widespread fear and politicisation of the issue.

A ministerial-level conference is being held in Geneva on Wednesday with the participation of UN Secretary-General Ban Ki-moon and U.N. High Commissioner for Refugees Filippo Grandi.

"The international context we are in - and nobody is naive about that - we know very well we're dealing with a complex situation, increasing fear in many countries, increasing politicisation of refugee, displacement and asylum issues. This is a difficult thing," UNHCR spokesman Adrian Edwards told a news briefing in response to a question.