The Afghan government has forced taxes on U.S. contractors appointed in the country, threatening new conflicts with the United States, the Washington Post reported.

The newspaper stressed, while citing unnamed Afghan and US officials, that taxation of US government assistance is banned by US law, as well as by a number of bilateral agreements between Afghanistan and United States.

However, the report said contractors have lately received tax bills for work done under the US government programs.

Reconstruction is a key component in an anti-rebellion effort led by the United States, which aims to even out the volatile south and east of Afghanistan as part of helping Afghan farmers and improving local government.

US Vice President Joe Biden pointed out on his second day surprise visit tn the war-torn nation last week that his country’s troops could remain after 2014 if Afghans want them to.

Around 97,000 troops from the United States are serving in Afghanistan as part of an international force of some 140,000.

The contractors have made an appeal to the Defense and State Departments to clarify the matter and according to the Washington Post, they have been told to ignore the bills and stand up for their rights.

However, the paper reported that Afghan government has already began sending overdue tax bills and has threatened some US companies with possible arrest, loss of licenses and confiscation of aid goods.

Afghan Finance Minister Omar Zakhilwal informed The Post through a text message that whatever is not exempted by law and treaties will not be exempted and that Afghanistan is serious against tax evasion.