Climate negotiators ended their first talks after last year's landmark Paris Agreement on Thursday with some delegates expressing concern about the potential impact of upcoming votes in the U.S. and Britain.

Britons will decide next month whether to remain in the European Union while Americans will elect a new president in November.

The 28-member EU has vowed to reduce greenhouse emissions by at least 40 percent by 2030 compared to 1990, but it's unclear what happens to that target if Britain, the bloc's second biggest emitter, leaves the EU.

"I'm sure there will be some parties saying 'without the UK can we still reach the at least 40 percent?'" Netherlands climate envoy Michel Rentenaar said at the U.N. talks in Bonn. "I think we can, but that would be decided by the remaining 27 member states."

Elina Bardram, the EU's chief negotiator, declined to speculate on how a British exit would affect the bloc's climate policy.

"We are ... confident that the British public will vote to remain in the EU," she said.

The Paris Agreement in December requires countries to submit plans for reducing or curbing their emissions and update them every five years.

Ajmad Abdulla, chief negotiator for small island nations at risk of rising seas, said he was confident the EU would "stick with their target" regardless of the outcome in the referendum.

A bigger unknown is what happens if Donald Trump, who has expressed skepticism about man-made climate change, wins the U.S. election. In 2012, he tweeted that "the concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive."

The Obama administration has pledged to slash U.S. emissions by 26-28 percent by 2025, compared to 2005 levels.

Mohamed Adow, a climate policy expert at Christian Aid, a Britain-based charity, said for the U.S. to backtrack on its Paris pledges would be "insulting," since key elements of the deal were designed to accommodate U.S. negotiators.

For example, the EU and others dropped demands for the targets to be legally binding so that the Obama administration could approve the deal without turning to Congress.

Nick Nuttall, a spokesman for the U.N. climate secretariat, said he couldn't imagine that any U.S. president would roll back efforts to cut emissions.

"In any political election there is a lot of talk but the reality of being in office is very different so I think we'll have to watch that space," Nuttall said.