Originally Posted by Track

The new line under construction in eastern France (to Strasbourg and for connections to Switzerland and southern Germany) is to be served by new TGV-R (French) and ICE-3 (German) trains. Top speed to Switzerland is to be 320 km/h and to Germany 300 km/h on both train types. 320 km/h is planned for the near future in eastern France on this route, and later 350 km/h will be the top speed.
Between Frankfurt and Cologne the German ICE-3s now run at a scheduled top speed of 300 km/h and can run up to 320 km/h to catch up on schedule delays. Some of these trains continue from Cologne into Belgium, where they compete with the French/Belgian/Dutch/German Thalys trains. Between Cologne and Aachen the top speed is 200 km/h, as this is not a new line but only an improved old line. In eastern Belgium a new line has been built for the Cologne-Brussels connection, with a top speed IIRC of 300 km/h.
The ICE-3 (not souped-up) has been tested up to 368 km/h and a souped-up TGV at a higher speed, but it did so much damage to the tracks and wires that no further tests were carried out.