The 28-year-old Rooney missed United's 4-0 win at Newcastle United on Saturday due to a toe injury, sparking fears that he could be forced to sit out Wednesday's return leg at Munich's Allianz Arena.

However, he took part in a light workout at United's Carrington training centre on Tuesday morning prior to the squad's departure for Germany, appearing to have no adverse reaction and to be in good spirits.

"Good training session with the lads ahead of the Bayern Munich match," he wrote on his Facebook page.

"It's a massive game for us against a top side but we'll be going in confident and looking to progress into the semi-finals."

Patrice Evra (knee), Ryan Giggs (groin) and Ashley Young (hand) also took part despite injury concerns.

Bayern coach Guardiola is positive Rooney will play against the European champions with the Munich tie delicately poised after last Tuesday's 1-1 draw in the first leg at Manchester's Old Trafford.

"He will play, I am 100 percent sure and I am willing to bet a large glass of beer on it," the Spaniard quipped during Tuesday's press conference in Munich.

"This is one of the best players I've seen play and the big players do not want to miss this type of game."

Rooney's presence in Munich will be a key factor for United with Netherlands forward Robin van Persie sidelined with a sprained knee and Juan Mata cup-tied.

Bayern have a few concerns of their own with Germany star Bastian Schweinsteiger and Spain's Javi Martinez both suspended, while attacking midfielder Thiago Alcantara is injured.

Winless in their last three matches, the Bavarian giants suffered their first Bundesliga defeat in 18 months when they were beaten 1-0 at Augsburg on Saturday.

Having taken charge in June, Guardiola admits failing to reach the Champions League's semi-finals with a defeat to Manchester United would be a mistake on his behalf.

European champions Bayern have already picked up three titles in Guardiola's nine months in charge, including securing the Bundesliga title with a record seven games to spare and remain 20 points clear in the table.

"If we don't reach the semi-finals, that is a big mistake by the coach," he said referring to himself.

"I'm aware of that, I knew it from the beginning after Bayern won the treble last season."

Guardiola said Wednesday's match will 'make or break' Bayern's season, but he expects the Bundesliga champions to be in Friday's semi-finals draw.

"It's now life or death in football and we'll still be alive on Thursday," said Guardiola.

"Of course, it is very important for a big club like this to be in the semi-finals. It's our dream."

The Spaniard dismissed both Bayern's Augsburg defeat and United's struggling Premier League form when asked if either were a yardstick for the Munich clash.

"This is a different competition," said Guardiola.

"They are fighting for a place in the Europa League, we are already German champions.

"Our goal for the last two, three weeks has been (to beat) Manchester United."

Guardiola said he is pondering reverting captain Philipp Lahm to right-back after the 30-year-old played in the defensive midfield role at Old Trafford.