"This year, even without Contador, we've got one of the strongest line-ups in the Tour of Spain's (73-year) history and we're expecting a wide-open, exciting event," Guillen told Reuters.

"Andy Schleck and Cadel Evans will be leading favorites from abroad. (Spaniards) Alejandro Valverde and Samuel Sanchez are also taking part, as well as sprint star Tom Boonen of Belgium.

"We'll miss Alberto but as soon as racing starts the fans will just concentrate on who's taking part," added Guillen.

Luxembourg's Schleck was runner-up in this year's Tour de France while Australian Evans was a podium finisher in Paris in 2007 and 2008.

Guillen said Saturday's start in Assen, only the second time the Vuelta begins abroad, will gain it much-needed international visibility.

"We started in Portugal in 1997 but this is the first time the race has ever begun north of the Pyrenees," he said.

"It's been long overdue and we will definitely be doing it again. This is a great place to start, Holland has more bikes than cars."

BANNED DRUGS

Guillen denied the race was due an imminent switch back to April and be cut in length from three weeks.

"We'd like a return to April at some point, those were the Tour of Spain's original dates up until 1995, but we're aware it's difficult," he said. "We're absolutely opposed to any shortening of the race."

Guillen said the Vuelta would take an aggressive stance on banned drugs.

"We're spending 250,000 euros ($358,000) on testing and we're working in full collaboration with the UCI (International Cycling Union," he said.

However Guillen added the race could not challenge the participation of Kazakh Alexander Vinokourov, racing in the Tour of Spain after a two-year ban for blood doping, or Valverde, who is suspended in Italy.

"Organizers aren't judges. If these two have their licenses in order and are authorized to take part, they can race," he said.

The tour also runs through Germany and Belgium before its biggest challenges are three straight mountain stages in Andalucia in the third week.

A 27.8-kilometer time trial in Toledo on Sept. 19 is likely to confirm the winner ahead of the finish in Madrid the next day.