Tour de France champion Tadej Pogacar won his first one-day classic on Sunday, snatching Liège-Bastogne-Liège victory on the line ahead of world champion Julian Alaphilippe who described the Slovenian as "a phenomenon".

The elite pair had been part of a five-man group who broke from the main pack on the day's final climb, with 13km left of a 259km slog over 11 tough climbs in the Ardennes.

The race marks the end of the Spring classics season with attention now turning to the Giro d'Italia starting May 8 in Turin and June's Tour de France, where Pogacar will be favourite to win again.

Pogacar, Frenchman Alaphilippe and his compatriot David Gaudu, Canada's Michael Woods and the 41-year-old Spaniard Alejandro Valverde managed to get away from the rest of the peloton atop the Roche-aux-Faucons climb.

It was then a cat-and-mouse affair across the lush fields outside Liège, with the veteran Valverde and Alaphilippe known as the fastest sprinters.

Valverde broke for the line early and was overhauled by Alaphilippe and Gaudu with 50 metres to go, before the 22-year-old Pogacar showed fresh legs, coming round from the back at lightning pace to grab victory right at the line.

Both men used the bike thrown technique at the line and Pogacar crossed first by half a wheel length.

"I sat on Alaphilippe's wheel in the run-in. I knew he could go for it from distance and I just managed to get him," said Pogacar who won the 2020 Tour de France with a penultimate-day assault.

Pogacar nearly missed the race after one of his teammates contracted Covid-19 in midweek and the entire UAE Emirates Team were ruled out of La Flèche Wallonne, won by Alaphilippe.

"I love this race," he said of Liège-Bastogne-Liège, the oldest of the 'Monument' one-day races.

"Now I will rest and get ready for the Tour de France," said Pogacar, who signed a deal worth five million euro per year with Team UAE in January.

Alaphilippe conversely must be sick of Liège after a second near-miss.

'Pitch perfect'

In 2020, he had raised his arms in victory before Primoz Roglic sped past him at the line with race officials later relegating him to fifth for blocking Pogacar.

But Alaphilippe was graceful in defeat.

"Tadej is a phenomenon, everyone knows that. From the moment he started to last year's Tour de France he's always been there at the big moments," he said.

"I'm quite happy with second all things considered. He was pitch perfect today. So hats off to him."

Movistar leader Valverde was celebrating his 41st birthday, and would have levelled the record number of five wins held by Eddy Merckx with a win.

It could all have been different as before the final climb, British outfit Ineos almost staged a coup by attacking from the Cote de la Redoute from over 30km out, as 2019 Giro d'Italia winner Richard Carapaz opened a gap after fine work from Tao Geoghegan Hart and Adam Yates.

But the Ecuadorian was caught outside Liège as Pogacar's UAE Team Emirates set up the winning move with a sudden attack of their own.

Carapaz was later disqualified after he was caught briefly sitting on his bike's crossbar when he was leading around 20km from the finish, a practice outlawed in cycling's rulebook from this month.

The 2019 Giro winner had crossed the line in 29th place, having enjoyed a 20sec cushion in his brief tenure as race leader.

Dutch rider Demi Vollering won the women's race ahead of compatriot Annemiek van Vleuten and Italian Elisa Longo Borghini.

The women's 140km race runs from Bastogne to Liège and takes in seven hills along the same narrow and winding Ardennes forest roads as the men, where it is notoriously difficult to keep track of the race.