Manchester United manager, Jose Mourinho is looking to strengthen his squad ahead of the new season. Photo: Jason Cairnduff/Reuters

Jurgen Klopp isn’t alone in noticing how grumpy Jose Mourinho has been on tour in the United States this summer.

Even by Mourinho’s sullen standards, it has been quite a performance.

‘One of my biggest goals in life is to make Jose smile — it doesn’t happen very often,’ was Klopp’s response after Mourinho said the Liverpool manager’s U-turn on big spending as ‘funny’.

Very little else has amused him on Manchester United’s joyless pre-season trek around America with half a squad and plenty more problems than Mourinho would have anticipated.

The main source of his frustration is United’s failure to deliver the signings he wants — and soon.

Not for the first time in his career, Mourinho is struggling to hide his impatience with his employers as Old Trafford chief Ed Woodward races to beat an early transfer deadline of August 9.

United open the Premier League campaign at home to Leicester City on a Friday night 24 hours later, a decision by Sky Sports that has also irked Mourinho.

His concerns that the start of the season will come too soon are understandable.

United have been without up to 12 World Cup players on tour, many of whom will not make an appearance here at all.

One of the few big names available to Mourinho, Alexis Sanchez, missed the first week of the trip because of visa issues. Another, Anthony Martial, made a sudden exit to be at the birth of his baby boy in Paris and has made it clear that he will not be coming back.

Captain Antonio Valencia has also gone, the victim of a calf muscle tear that will keep him out of the start of the season. New £19million signing Diogo Dalot cannot replace him because he is unavailable until September as he recovers from a knee injury.

Mourinho wants at least two more signings — ideally a centre-back and a forward — but has been told by Woodward that United must sell before they buy.

Martial and Marcos Rojo are the two who have been earmarked to go, but offloading them for the right price in time to bring in replacements before the window closes will not be easy.

No wonder Mourinho has been at his malevolent worst in the US.

The 55-year-old is unhappy with the quality of squad available to him and their performances so far as United have recorded three rather pointless draws against Club America, San Jose Earthquakes and AC Milan in front of disappointing attendances.

United’s game against Liverpool in the early hours of this morning was expected to buck that trend, with a crowd of around 100,000 expected in Michigan, but this has largely been a pre-season tour to forget.

Mourinho has moaned about the lack of first-team players after the World Cup.

Given the chance to praise Paul Pogba’s success at the tournament in Russia, there has been only more thinly veiled criticism of a player he believes can offer so much more for his club.

When asked if United have the squad to challenge for the title this season, Mourinho’s refusal to answer was telling.

Maybe his mind is going back to the summer of 2015, when a poor transfer window and awful start to the season cost Chelsea dear. Mourinho was sacked by Christmas, just seven months after winning the title, with the champions in 16th place.

There are shades of that summer now in his disaffection with the board and murmurings of discontent in camp.

A coach who has never stayed much longer than three years at any of his previous clubs is entering his third season at Old Trafford in less than great shape.

Mourinho continues to live a hotel existence in the Lowry, away from his family in London, and can no longer call upon the support of his trusted lieutenant, Rui Faria, who left United at the end of last season. The two had worked together for 16 years, and the impact of Faria’s departure — both as a coach and confidante for Mourinho — should not be underestimated.

It is building up to be a crucial season for United and their manager.

A prosaic style of football was tolerated when he started out by winning the Europa League, League Cup and Community Shield in his first year in charge at Old Trafford.

But the frustration among supporters was palpable as a swashbuckling Manchester City swept to the title last season, leaving United 19 points behind in their wake.

They simply cannot afford a slow start this time around, and Mourinho knows it.

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