Congressional aides say 59 senators now back a sanctions bill they say would increase the pressure on Iran to make nuclear concessions.

The Obama administration says the legislation risks scuttling a historic opportunity to resolve Iran’s nuclear standoff through diplomacy instead of military action.

Senators in favor include every Republican except Jeff Flake of Arizona and Rand Paul of Kentucky.

Sixteen Democrats are on board including Sen. Chuck Schumer of New York, a top ally of President Barack Obama.

Only 26 senators co-sponsored the bill when it was introduced last month.

The new count brings sanctions proponents to the brink of being able to pass the bill. The House overwhelmingly supports more sanctions.

The White House has threatened to veto any such bill. Sixty-seven votes are needed to override.

(AP)