The Senate on Thursday rejected a proposal by Sen. Tom Coburn to tie some student loan rates to the market rate for Treasury bills, while also turning down a competing proposal to keep the current rates stable.

The gridlock comes just weeks before interest rates for Stafford loans are set to double from 3.4 percent to 6.8 percent.

The proposal by Coburn, R-Muskogee, and three other Republican senators would link the rate for subsidized Stafford and PLUS loans to the rate on 10-year Treasury bills and add three percentage points to cover costs. At the May 15 auction rate of 1.75 percent, the rate for the next academic year would be 4.75 percent.

President Barack Obama and House Republicans have also proposed that some student loan rates be linked to Treasury bill rates, though details differ.