UNITED NATIONS (Reuters) - There are concerns at the United Nations about apparent attempts inside the United States to “sabotage” President Barack Obama’s commitments to reducing greenhouse gas emissions, the head of the U.N. General Assembly said on Wednesday.

Mogens Lykketoft, president for the UN General Assembly, speaks after Pope Francis addressed a plenary meeting of the United Nations Sustainable Development Summit 2015 at United Nations headquarters in Manhattan, New York, September 25, 2015. REUTERS/Mike Segar

Mogens Lykketoft of Denmark, current president of the 193-nation General Assembly, issued the warning in an interview with Reuters ahead of Friday’s U.N. signing ceremony for the Paris agreement aimed at slowing climate change.

Both China and the United States, the world’s top emitters accounting together for 38 percent of emissions, have promised to sign then. U.S. Secretary of State John Kerry is expected to attend.

With a U.S. presidential election just months away, Lykketoft warned that there appear to be forces at work in the world’s biggest economy aimed at undermining the historic climate deal.

“What scares us a little ... is there is all this sabotage inside the United States against this commitment for climate change, including (with) the Supreme Court,” he said.

Lykketoft was referring Obama’s difficulties in replacing U.S. Supreme Court Justice Antonin Scalia, who died earlier this year.

Obama has nominated centrist appellate Judge Merrick Garland to replace Scalia. But the seat may remain empty for around a year as Senate Republican leaders insist that Obama’s successor, who will take office next January after the Nov. 8 presidential election, fill the vacancy.

“Seen from a climate (agreement) implementation point-of-view, it’s very important how it plays out in the elections in the United States, including the selection of the missing member of the Supreme Court,” Lykketoft said.

He said he was not taking a partisan position in the election, but added that the next U.S. leader should not be someone intent on backtracking on the Obama administration’s commitments.

“If the United States of America is not playing a constructive role here, we will almost certainly not reach the goals, because it’s such a huge economy,” he said, adding that it was “crucial that there is non-denier on climate (change) as the American president.”

Any Republican president might seek to undo Obama’s domestic plans to cut emissions by 26-28 percent by 2025 below 2005 levels, he said. And plans by Obama, a Democrat, to cut emissions from power plants could also face legal challenges that end up being decided by the Supreme Court.

More than 130 nations with 60 leaders including French President Francois Hollande are due to sign the Paris deal on Friday, the most ever for a U.N. agreement on an opening day.