TIGERSHARKS' Jazz Carlin came through fifth-fastest in her 800m heat this morning and will now face off with the USA's Katie Ledecky in tomorrow's World Championship final in Kazan.

Carlin, who is the European champion at the distance, led the first 200m of heat four alongside Australia's Jessica Ashwood.

At the halfway stage, Carlin extended her lead by 1.25s, but eased up slightly as Ashwood moved ahead by the slightest of margins on the 600m mark.

In the final 50m, Ashwood pulled away from Carlin, who faded to finish second in a time of 8:23.83.

In the last heat of the session, Ledecky started under the world-record time in the first 100m and managed to keep up the pace until the halfway mark, where she began to ease off, finishing in a time of 8:19.42, 4.41 quicker than Carlin.