Thornburg, which is based in Santa Fe, N.M., has been beset by "margin calls," or lenders demanding their money back.
The company reached a deal under which its lenders would stop issuing margin calls if Thornburg raised $948 million.
A bond sale arranged to raise money at a 12 percent interest rate failed, and now the company is trying to sell $1.35 billion in bonds at an 18 percent interest rate.