THE Trump administration has rejected a carbon tax on shipping and has vowed "reciprocal measures" to shield US ships such duties according to a letter seen by Politico, of Arlington, Virginia.

The UN's International Maritime Organisation's (IMO) Maritime Environmental Protection Conference (MEPC) is taking place in London this week and aims introduce and green tax on shipping.

The US letter, which intends to block the tax, was circulated to many embassies of IMO member states.

The letter said: "President Trump has made it clear that the US will not accept any international environmental agreement that unduly or unfairly burdens the US or the interest of the American people."

The debate at the MEPC is whether to tax shipping emissions through a fuel standard (a carbon credits trading scheme) or a universal levy (a flat-rate tax on emissions).

"Accordingly, we must be clear the US rejects any and all efforts to impose economic measures against its ships based on emissions or fuel choice," the letter said.

"Should such a blatantly unfair measure go forward, our government will consider reciprocal measures so as to offset any fees charged to US ships and compensate the American people for any other economic harm from any adopted GHG emissions measures. The Trump Administration will protect the American people and their economic interests.

"The UN should halt all efforts to proliferate the deeply unfair agenda reflected in the Paris Agreement in other fora," adding that "a plain reading of these measures is that they are foremost an effort to redistribute wealth under the guise of environmental protection."