Why $1bn in Balkans energy contracts are going to an obscure company connected to Donald Trump

Guardian investigation shows how US presidency blurs line between policy and enrichment of American ruling family and those around it

On a graffitied Sarajevo backstreet, a path leads past an overgrown patch of garden to a white door. Beyond is the registered office of a company that is on the brink of winning contracts worth more than $1bn.

AAFS Infrastructure and Energy is close to securing a concession to build and operate a pipeline across the Balkans to allow fossil gas shipped from the US to replace supplies that come from Russia. “This could be the most important infrastructure project ever in Bosnia and Herzegovina,” says one of the country’s top officials, who, like others, asks to remain anonymous to discuss sensitive negotiations.