Under-fire Wenger rallies troubled Arsenal

But captain Per Mertesacker admitted to tension in the dressing room and said his struggling team haven't shown enough fight, as they seek to pull off the improbable and overturn a 5-1 first-leg deficit.

The 28-year-old Sanchez was reported to have stormed off the training pitch last week before becoming involved in an angry confrontation with his team-mates, but he took part in training on Monday and shook hands with manager Wenger before the session.

Sanchez started Saturday's 3-1 Premier League defeat at Liverpool on the bench, coming on at half-time and creating a goal for Danny Welbeck.

Asked about the reports at a press conference prior to Tuesday's last-16 second leg at the Emirates, Wenger said they were "completely false".

"Nothing happened, nothing at all," Wenger said.

"But I understand that you have to fill the newspapers and we respect that. When you don't win the games there are sometimes stories."

Wenger said his relationship with Sanchez was "honest and normal, like with every single player" and played down the possibility that the Chile forward might leave during the close season.

"Alexis Sanchez has 15 months on his contract so the decision on whether he stays will depend on Arsenal Football Club, not on anybody else," said the Frenchman, refusing to be drawn on whether Sanchez will start the game against Bayern.

Key midfielder Mesut Ozil looks set to miss out after illness.

Sanchez -- like Ozil -- has been linked with a move away from Arsenal at the end of the season, with Juventus and Paris Saint-Germain among the clubs reported to be monitoring the situation.

A July 2014 signing from Barcelona, Sanchez is Arsenal's top scorer this season with 20 goals in all competitions and is seen as their most important player alongside German playmaker Ozil.

But as Arsenal's form has dipped, his on-pitch displays of frustration have become increasingly noticeable.

Arsenal slipped out of the Champions League places following the weekend loss at Liverpool, a third defeat in their last four Premier League games.

- 'Ready to fight' -

Mertesacker refused to be drawn on suggestions that Sanchez has become isolated from the rest of the squad after apparently criticising his team-mates following the Bayern first-leg thrashing.

But the defender admitted there was a fraught atmosphere in the squad.

"It's a little bit tense but it's normal in a stretch like that. We want to change it and you can feel that in every training session," the German said.

That prompted Wenger to insist he still retains his squad's support: "We are not in a political club here, it's about performance. The players are ready to fight.

"We live in a world of small margins. On the confidence front it can look like you don't want to fight, but I believe 100 percent that these players want to win and do well."

Unfortunately for Wenger and Arsenal, Bayern arrive in red-hot form with 20 goals in their last five games, including Saturday's 3-0 league victory against Cologne.

Bayern could repeat their 2013 treble of Champions League, Bundesliga and German Cup and are in pole position for a fifth straight title in Germany's top flight.

Franck Ribery came off the bench to score Bayern's last goal in Cologne and the French winger said Carlo Ancelotti's team are eager to finish off what they started in the first leg.

"The atmosphere is very good. We are playing like a real team," Ribery said in comments that contrasted with the picture Mertersacker painted of Arsenal.

"We want to achieve something together. I have always said, when we want to win lots of titles, we need every player.

"We can't win every game 3-0, but we have to keep playing like that. We have an important three months ahead of us."