WASHINGTON (Reuters) - President Barack Obama's decision to delay implementation of part of his healthcare reform law will cost $12 billion and leave a million fewer Americans with employer-sponsored health insurance in 2014, congressional researchers said Tuesday. The report by the non-partisan Congressional Budget Office is the first authoritative estimate of the human and fiscal cost from the administration's unexpected one-year delay announced July 2 of the employer mandate - a requirement for larger businesses to provide health coverage for their workers or pay a penalty. The analysts said the delay will add to the cost of "Obamacare's" insurance-coverage provisions over the next 10 years.