A senior United Nations official has called on Japan to help reform the global body, saying Russia's invasion of Ukraine has deepened divisions among member states and made it difficult to resolve disputes.

Elizabeth Spehar, assistant secretary-general for peacebuilding support, spoke to NHK in Tokyo on Thursday. She heads the UN Peacebuilding Support Office.

Spehar said the UN is trying to support Ukrainians, exploring possibilities such as humanitarian responses, prisoner exchanges and dialogue.

But she said the UN "is only as strong as its member states will allow." She stressed the need to "strengthen the UN" to enable it to deliver on its responsibilities.

She said the Security Council is now "definitely experiencing challenges" and "has not always frankly been up to the task." She called for reform, saying conflicts across the world are becoming difficult to resolve.

Spehar also spoke about Japan becoming a non-permanent member of the Security Council from January.

She said it's "very opportune" to have Japan as a council member because the country is "a strong supporter of the UN" and has "very strong peacekeeping credentials."

She said she hopes Japan takes a leadership role in peacebuilding efforts and UN reform.