Washington: Congress' budget analysts are putting a USD 1.2 trillion price tag on a long-term plan to modernise the US nuclear arsenal that President Donald Trump inherited from his predecessor.

The Congressional Budget Office says in a report yesterday the costs will accumulate over the next 30 years as existing weapons now considered outdated are replaced. Trump pledged during the campaign to overhaul the nuclear arsenal. He moved ahead after taking office with an Obama administration strategy to develop, build and field new submarines armed with nuclear missiles; new nuclear-capable bomber aircraft and a new fleet of land-based intercontinental ballistic missiles.

Representative Adam Smith of Washington, top Democrat on the House Armed Services Committee, says "Congress still doesn't seem to have any answers as to how we will pay for this effort."