The Obama administration has made a first installment on its $3bn pledge to help poor countries fight climate change – defying Republican opposition to the president’s environmental plan.

The $500m payment to the Green Climate Fund was seen as critical to shoring up international confidence in Barack Obama’s ability to deliver on the pledges made at the United Nations’ climate change conference in Paris in late 2015.

Obama is expected to announce a number of joint climate initiatives when Canadian prime minister Justin Trudeau visits Washington this week, sources familiar with the plans said.