A new analysis showing the legislation would be far more expensive than the House version could complicate its chances of final passage in that chamber, where fiscal hawks have said the cost must not grow.

Debate is underway in the Senate for an all-night session Sunday, with Republicans wrestling President Donald Trump's big bill of tax breaks.

The bill, containing tax breaks and spending cuts, would be a signature achievement for President Trump. But some Republican senators have concerns that have not been resolved.