Carlo Ancelotti insisted Real Madrid deserved to defeat Barcelona as the Los Blancos coach questioned the late VAR decision to rule out Marco Asensio's' goal in Sunday's 2-1 Clasico loss.

Substitute Asensio thought he had snatched a late winner at Camp Nou, turning home from Dani Carvajal's cross in the 81st minute before a lengthy VAR check adjudged the Spain international to be offside.

Franck Kessie coolly finished past Thibaut Courtois 11 minutes later as Barca grabbed a last-gasp victory to move 12 points clear at the summit of LaLiga.

Ancelotti was unconvinced by the decision to disallow the goal for Asensio, who was deemed to be in front of Jules Kounde, but lauded a resilient Madrid performance on Sunday.

The Italian said to Movistar: "You have to accept [the decision]. But I'm left with doubt. Surely there is nothing. We have the right to have that doubt.

"We played a good game, we deserved to win, it was won. Then there is the question of this goal that was disallowed.

"We tried everything at the end, we lost a bit of balance and they scored. The game was very good, we leave with the confidence that we can finish the season well."

With 12 league games left to play after the international break, and a two-legged Champions League quarter-final against Chelsea to follow in April, Ancelotti vowed Madrid will battle until the end.

"We are going to fight for all competitions, to the maximum," he added. "We have to try to play like this again. If we play like this we will win something, for sure."

Defeat to Barca came just four days after the Champions League last-16 victory over Liverpool and Ancelotti suggested Madrid are suffering from a gruelling schedule.

"We have a greater disadvantage than before and it is even more difficult, but we are going to play until the last game," he told reporters at his post-match press conference.

"The plan did not change with the substitutions we made, only the individual characteristics change, such as [yellow] cards, suspensions and fatigue."

Ancelotti also acknowledged Madrid's title charge was hampered by a disappointing return to club action after the mid-season World Cup break.

"January has cost us a lot because after the World Cup it was difficult for us to recover our condition," he continued.

"But we are going to finish the season well. Today the game was good, with a good approach, with good changes."