A Senate sponsor of a climate and energy bill said during a televised interview last weekend that supporters are still short of the 60 votes they need to advance the legislation.

About 50 senators support the bill while 30 others oppose it, said Senator Joe Lieberman. That leaves 20 or so senators undecided.

A major sticking point has been the bill’s approach to carbon emissions, which are blamed for global warming. Lieberman said capping carbon pollution and putting a price on it is at the heart of the bill. Republicans reject the idea of a carbon tax.

President Barack Obama has called a bipartisan meeting to discuss the climate bill and other energy matters mid-week.