Washington (CNN) Afghan leader Ashraf Ghani wrote a letter to President Donald Trump offering to look at how to reduce the costs of keeping US troops in Afghanistan.

It was given to Ambassador Alice Wells on Tuesday but it is unclear if the letter has yet been delivered to the White House or read by Trump, according to two sources who have seen the letter.

Afghan officials have been discussing how to handle a possible US withdrawal and they were aware that cost-saving would be attractive to Trump.

However, the letter did not propose a specific cost or troop reduction, but rather, suggested engaging in conversations about how costs and troops could be reduced, sources told CNN.

The letter did not suggest a specific time for the meetings on these topics to take place but said they should happen in the "near future," the sources added.

Read More