As the UN General Assembly meets this week, economist Bjorn Lomborg suggests that America keep its checkbook closed until the world body sets reasonable spending priorities.

Secretary-General Antonio Guterres demands a “tripling” of global development aid — “at least $500 billion for the rest of decade” — to ignite progress on the UN Sustainable Development Goals wish list.

Problem is, the list is full of fantasy and relative frivolity, with goals like promoting lifestyles “in harmony with nature” and adding urban parks for the disabled, along with utopian stuff like ending war.

It’s a compilation of interest-group asks, not a cost-effective list of realistic priorities: 169 “targets” in total.

Of course the United Nations, and the world, winds up falling short on all of them — and will achieve none of them by the 2030 target date.

A UN report, Lomborg notes, shows: “On current trends, only one-third of countries will achieve their poverty promises by 2030, and 300 million children and young people will still leave school unable to read or write.”

Even though Uncle Sam spends more than $60 billion a year on humanitarian aid to other nations, with the US private sector kicking in another $30 billion.

And tripling those outlays as Guterres demands still wouldn’t come close to turning the tide — nor even do much good if spent as he and his UN minions suggest.

The grim truth is that most government-to-government aid gets wasted, by corruption and on failed policies like reducing class sizes.

This doesn’t mean spending nothing to help the rest of the world, but it does point to redirecting what America does spend, and not giving the UN a blank check.

US philanthropists — and Congress — could do a lot worse than focus this giving on the dozen cost-effective development policies identified by hundreds of economists and seven Nobel Laureates for Lomborg’s Copenhagen Consensus.

Be generous, but not stupid.