A key round of climate negotiations opened in Bonn on Monday with a top UN official warning there was not enough money to host the year-end Paris conference tasked with sealing a global carbon-curbing pact.

There was insufficent "funding for participation for either the October session, which is already planned, or for the COP," UN climate chief Christiana Figueres told delegates, referring to the next scheduled negotiating round, and the November 30-December 11 Conference of Parties (COP).