Republican Senator Paul threatens 'no' vote on budget plan

"I have told the White House and (Republican) leaders that if they simply stick to their own caps, the rest of the budget is fine and I'll vote yes," Paul wrote on Twitter. "It is a simple, but important, change they could easily make. The ball is in their court."

Republican leaders can afford to lose only two Republican votes on the budget plan, which would pave the way for large-scale tax cuts, if Democrats remain united in opposition. With Senator Thad Cochran out of town for health reasons, a defection by Paul would leave the vote on a razor's edge.

(Reporting by Tim Ahmann; Editing by Doina Chiacu)