Russia will discontinue the use of the uprated Soyuz U2 booster for launches of manned Soyuz TM and other craft into low-Earth orbit, and revert to the sole use of the Soyuz U, because of budget difficulties. The Soyuz U2 had more redundant systems and used a more expensive synthetic fuel. It had been used for 47 launches, all successful. The launches of the TM23 and 24 craft were on the original Soyuz U.
Source: Flight International