Thursday's Europa League round-of-32 first leg against St Etienne kicks off a frantic 11-day period for United as the second leg in France comes after an FA Cup tie at Blackburn and is followed by the EFL Cup final against Southampton.

There will be little let-up if United emerge victorious from that run of matches as more fixtures would leave them with a packed schedule.

Mourinho believes balancing domestic and European commitments will stretch his squad and ultimately hamper their chances of success, though he is not allowing them to take their foot off the gas.

"We cannot choose the competitions at Manchester United,'' he told a news conference. "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.''

Mourinho is desperate to return United to the Champions League, but believes qualification through the Premier League will be harder to secure than for other teams as cup progress will "create many, many problems."

"We know that it's going to be very difficult,'' Mourinho said, with just four points separating sixth-placed United and second-placed Manchester City. "We know obviously it can have an impact in the Premier League because we are competing against teams in other circumstances.

"For example, Liverpool play only in the Premier League, Chelsea in the Premier League and the FA Cup. We have still Tottenham in a similar situation as us, but we want to progress. That's the point.

"We prefer difficult but progressing to easy and being knocked out of the competitions. We will go seriously tomorrow and seriously against Blackburn on Sunday.''

Luke Shaw will be hoping to be involved at Ewood Park having been overlooked for Thursday's match, while Phil Jones, out with a foot complaint, will want to face his former club.

Wayne Rooney and Michael Carrick will not be risked against St Etienne, but Mourinho plans to name a strong side.

Thursday's match pits United midfielder Paul Pogba against his older brother Florentin, leaving the Pogba family hoping for a draw.

"We spoke in a good way, a funny way,'' Mourinho said of Paul. "I think it is a good, nice destiny. I think only mum Pogba is a little bit in trouble, which is normal. It's difficult for the lady to choose -- it's not difficult, it's impossible.

"I know from Paul that the mum wants a draw, but next week one son will be happy and another one will be sad. But I think for the mum it's a bit of a problem, but they will enjoy playing against each other. Paul is excited, Florentin for sure the same. I think it's a good thing.''