US President-elect Donald Trump was at the receiving end at the UN-led climate change talks in Morocco, with countries saying he risked isolation should he pull his country out of efforts to reduce global warming.
UN Secretary General Ban Ki Moon said he hoped Mr Trump will make the right decision when he assumes office next year.
"I hope he will understand the seriousness and urgency of addressing climate change. I already spoke to him on the telephone and I look forward to meeting him in person," the Secretary General told a media briefing at the ongoing UN-led climate change conference in Marrakesh, Morocco, on Tuesday.
Mr Trump has dismissed climate change as a hoax, saying he would pull the US out of subsequent climate negotiations.
Ban said progress by countries to seek a global solution was impressive and that political leaders were duty-bound to support the processes. He warned that no county, however powerful or rich, was immune to climate challenges.
"We have seen in many countries, not just the US. Campaign rhetoric may not be implemented. I am sure Mr Trump will make the right decision," he said when asked what the UN's next course of action would be if Mr Trump pulls the US of the Paris agreement.
The historic Paris agreement was signed last year where countries agreed to limit global warming to 2C above pre-industrial levels. It came into force this month and its implementation will require cuts in use of fossil fuels. It was backed by 200 nations and ratified by 109.
The Secretary General spoke as developing countries added their voice to the Trump issue, saying any drastic action by the new US leader could stifle the Paris deal and pull back gains, the same fate that befell the Kyoto protocol after it failed to get the US senate's nod.
Chairman of the Least Developed Countries Tosi Mpanu-Mpanu said: "If the US leaves the boat, other parties will carry on but it will be a shame."
He added: "I don't see in any way why Mr Trump should work to hinder this agreement. But even if it becomes true, no party should be allowed to obstruct the political goodwill we have seen since Paris."
Mpanu-Mpanu, however, expressed confidence the process would yield a favourable outcome. He said: "We cannot pre-empt the outcome. We can only be optimistic."
US Secretary Of State John Kerry, who is expected in Marrakech, has downplayed possibilities of the US pulling out, saying climate vagaries were evident and the US will honour its international obligations.
Kerry said: "We will wait to see how the next administration addresses this."
But as concerns emerged that Mr Trump could jolt the Paris agreement, President Barack Obama's administration said it had invested US$11 billion in international clean energy finance – including grant-based assistance, development finance, and export credit – to support countries meet their growing energy needs.
"The US has made research and development a top priority, decreasing the cost of clean energy technologies substantially, and has launched several initiatives to enhance universal access to affordable, reliable, and cleaner energy globally," said a statement released yesterday by the US negotiators at COP22.
Secretary General of the United Nations Framework Convention on Climate Patricia Espinosa, however, said she was looking forward to a productive engagement with Mr Trump. "Where we are now, the process is unstoppable," she said yesterday.
Experts say while Mr Trump cannot force other countries to abandon the Paris deal, he can weaken efforts by US to reduce emissions. And without the full participation of the US, which is a top polluter after China, efforts to cut emissions would come to naught.
Legally, he could withdraw in four years as per Article 28 of the Paris accord but insiders say he could seek a shorter exit route, including sending a withdrawal letter or placing a presidential order to withdraw the US.
But as COP22 gets underway, the world will be waiting to hear Mr Trump pronounce himself on his game plane on climate change after his inauguration in January next year.