JOSE Mourinho has vowed his Manchester United side will field a strong team against Blackburn Rovers in Sunday's FA Cup fifth round clash - even if it leads to fixture pile up later in the season.

Ahead of tonight's Europa League last-32 first leg clash against St Etienne, Mourinho said United will end up "in trouble" if they continue to fight on all fronts.

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But the Old Trafford boss said he would not allow his side - who are also in the EFL Cup final next week and continue to fight for a top four spot in the Premier League to take their foot off the gas.

"We cannot choose the competitions at Manchester United," the United boss said. "We know that our situation is really complicated.

"We know that the Europa League is also a competition where we play on Thursdays and that makes it even more difficult for us.

"The accumulation of FA Cup, League Cup, match postponements is really hard for us.

"If we progress in the competitions, we will be in trouble in April and May. But we cannot choose competitions, so we play them to win.

"I think it's also a good way to give the team experience and international experience is always a plus.

"Europa League is not a competition we want to play, but it's a competition we play and we respect it.

"We prefer difficult but progressing to easy and being knocked out of the competitions.

"We will go seriously (against St Etienne) and seriously against Blackburn on Sunday."