The move raises fresh doubts over whether the Senate this year can pass climate legislation. If not, US credibility would likely suffer at UN-led negotiations aimed at reaching an international treaty that mandates carbon emission reductions through 2050.

Lindsey Graham, a South Carolina Republican, who has been working on the bill with Kerry and Joe Lieberman, a Connecticut Independent, lashed out at top Senate Democrats and the White House for suddenly wanting to rush immigration reform ahead of climate change with an eye on November mid-term elections.