The ongoing UN climate conference began its high-level talks here on Tuesday, after the first week of meetings made little progress.

Heads of states or governments or ministerial delegates from over 190 countries are participating in the second phase of talks which runs until Friday.

UN Secretary General Ban Ki-moon, speaking at the opening ceremony, urged participants to "sustain the momentum for change so painstakingly built in Bali, Poznan, Copenhagen, Cancun and Durban."

Pointing to water stress, land degradation, melting icecaps, Ban said "we are in a race against time to stay below the agreed threshold of 2 degrees Celsius above pre-industrial levels that will avoid the worst impacts of climate change."

Qatari Emir Sheikh Hamad bin Khalifa Al-Thani attended the opening ceremony and highlighted the importance his country attaches to averting climate change and protecting the environment.

The emir also pledged Qatar's contribution to green technologies which can help strike an optimum equilibrium between the need for energy and emission reduction.

Present at the opening ceremony were Christiana Figueres, executive secretary of the UN Framework Convention on Climate Change, and Vuc Jeremic, president of the UN General Assembly, among other dignitaries.

The high-level segment, running until Friday, is expected to undergo intensive talks and overnight meetings as nations need to close their differences on core issues, including the second commitment period of Kyoto Protocol and finance support to developing countries. Endi