* Green Climate Fund's biggest payment so far to U.S. group
* Trump says GCF costing a "vast fortune"
* GCF work delayed by legal red tape
* Board members reject Trump's criticisms of GCF
By Heekyong Yang, Jane Chung and Alister Doyle
SEOUL/OSLO, June 13 (Reuters) - The $10 billion Green Climate Fund that U.S. President Donald Trump said was a waste of tax dollars has fallen behind on its goals, with a biggest payout so far of just $5 million for a U.S.-led solar energy project.
Work at the international fund, which aims to help poor nations cut greenhouse gas emissions and adapt their economies to heatwaves, storms and rising seas has been slowed by legal red tape and the approval process, board members say.
The GCF, whose South Korean headquarters opened in 2013, says it only approved projects worth $1.3 billion in 2016, short of its goal of $2.5 billion. It has approved total loans and grants worth $2.2 billion. All but $13 million is still in the bank.
GCF officials declined to comment on Trump's remarks or elaborate on the slow pace of approvals, deferring to the 24 board members who represent both developed nation donors and developing nations that will receive funds.
"On disbursement, my own personal view is that it's appalling," said Zaheer Fakir, a board member from South Africa.
Announcing on June 1 that the United States was quitting the 2015 Paris climate agreement, Trump said he was halting U.S. contributions to the GCF after $1 billion paid under former President Barack Obama, who had pledged a total of $3 billion.
Trump, who says climate action will cost U.S. jobs and wants to promote the U.S. coal industry, said the fund cost taxpayers a "vast fortune" and many other nations "will never pay one dime."
Reuters contacted five current and former board members, who said they did not agree with Trump's comments. They acknowledged the fund had been slow to get going but said it was difficult to get projects off the ground and unreasonable to expect big flows of money straight away.
"The fund is like a plane that's taken off but we're still building it in mid-air. That's a risky situation," said another board member who did not want to be named.
NO SLUSH FUND
More than 40 nations in 2014 promised a total of $10.3 billion to the GCF, including Obama's $3 billion.
Washington's $1 billion is the biggest single contribution so far. But Sweden's $581 million, for instance, works out as $60 per capita, against $3 per American. Japan has promised $1.5 billion.
The board members also say the 2016 project approval goal had been largely aspirational to encourage nations to step up climate finance. Fakir said that the board sometimes lacked time to consider projects in detail and developed countries often attached too many conditions to loans.