WALES' Euro 2004 qualifying hopes could suffer a major blow as big targetman John Hartson has fresh injury problems which might rule him out of their crucial Group Nine showdown in Serb-ia/Montenegro.

The Celtic striker was making steady progress in his rehabilitation from a back problem, but now the 28-year-old has been knocked-back with a calf problem and he's a major doubt for Wales' Belgrade date two weeks tomorrow.

Hartson, the focal point for Mark Hughes' resurgent unbeaten Welsh table-toppers, missed Celtic's end-of-season run-in, including the UEFA Cup final, with a back problem which required an operation.

Hartson was hoping to return in time for the second leg of Celtic's Champions League second qualifier against FKB Kaunas tomorrow - but it is feared this latest misfortune will knock him out for weeks.

That would be enough for him to miss Wales' trip to the Balkans on August 20 and mean Hartson will face a race-against-time to be fit when Hughes' men come face-to-face with the mighty Italians, second in Group Nine, in a winner-takes-all clash in Milan on September.

A Celtic statement today read: "He (Hartson) continues to progress well in his rehab work, with the club's medical staff happy that his back has healed, but he has been suffering from stiffness in one of his calf muscles."

Welsh boss Hughes would want Hartson to have played a first-team game for Celtic before he links up with Wales to improve his match-fitness.

And Hughes knows Hartson would be a great loss, saying: "He's larger than life, a leader who can have an impact on the game at the highest level."

Tottenham Hotspur play-maker Simon Davies (calf) and Aston Villa right-back Mark Delaney (knee) have responded well to treatment are likely to be fit for the new season.

But Fulham centre-back Andy Melville, who is struggling with an ankle injury, is 'touch and go' for the Serbia clash in Belgrade's Red Star Stadium.

The 58-times capped 34-year-old, Wales' longest-serving player, has missed most of Fulham's pre-season with ankle trouble and is a serious doubt for the start of the Premiership season, which starts on Saturday week.

Wales squad: D Coyne (Leicester City), M Crossley (Middlesbrough), P Jones (Southampton), D Ward (Nottingham Forest), D Barnard (Grimsby Town), C Bellamy (Newcastle United), N Blake (Wolverhampton W), S Davies (Tottenham Hotspur), M Delaney (Aston Villa), R Earnshaw (Cardiff City), D Gabbidon (Cardiff City), R Giggs (Manchester United), J Hartson (Celtic), A Johnson (WBA), J Koumas (WBA), A Melville (Fulham), J Oster (Sunderland), R Page (Sheffield United), M Pembridge (Everton), C Robinson (Portsmouth), R Savage (Birmingham City), G Speed (Newcastle Utd), K Symons (Crystal Palace), G Taylor (Burnley), P Trollope (Northampton Town), R Weston (Cardiff City), A Williams (Reading).