US troops in Afghanistan now number about 8,400, a far cry from the US presence of more than 100,000 six years ago.
The statement called for the complete withdrawal of foreign forces from the war-torn country and comes as Trump weighs increasing the number of American troops there.
"Previous experiences have shown that sending more troops to Afghanistan will not result in anything other than further destruction of American military and economical might."
"Therefore it would be wise if you adopt the strategy of a complete withdrawal from Afghanistan instead of a troops increase," said the English-language letter, which was sent to the media."
US troops in Afghanistan now number about 8,400, a far cry from the US presence of more than 100,000 six years ago. They mainly serve as trainers and advisers to Afghan forces.
Trump's administration is currently finalising a new policy for Afghanistan almost 16 years after the US invasion to topple the Taliban regime.
American military commanders in Afghanistan have requested thousands of extra boots on the ground to help combat a resurgent Taliban.
Defense Secretary Jim Mattis is believed to be close to presenting the new US military strategy to Trump, with an announcement potentially coming in weeks.
The Taliban, which ruled Afghanistan from 1996-2001, also slammed the Afghan government in the letter and warned the United States that it could never defeat the insurgent group.
"It is entirely possible that you are being provided rosy pictures about Afghanistan by the stooges you have installed," it said.
"You must realize that these repulsive sellouts neither care about your interests nor that of their own nation," the statement added.
The letter described foreign occupation as the "main driver of war" in Afghanistan and ended by making reference to reports that Trump may be considering outsourcing operations to private contractors.
In recent months, Erik Prince -- founder of the private security company Blackwater -- has resurfaced with an offer to send a private army of around 5,500 contractors to replace the US troops.
"If you failed to win the Afghan war with disciplined US and NATO troops... you shall never be able to win it with mercenaries, notorious contractor firms and immoral stooges," it said.