Manchester United beat Athletic Bilbao 4-1 in the Europa League to complete an emphatic 7-1 aggregate semi-final victory, setting up a mouthwatering showpiece against Tottenham.

Fireworks crackled and red smoke filled an expectant Old Trafford following an impressive 3-0 win against 10-man Athletic in northern Spain last week.

But the air of excitement was tinged by the knowledge that Ruben Amorim's United have shown a startling ability to implode during a horrendous Premier League season.

Amorim reverted to the team that started in the first leg, making eight changes following Sunday's 4-3 defeat against Brentford.

Dani Vivian was suspended after his red card last week and coach Ernesto Valverde was also hamstrung by the absence of brothers Nico and Inaki Williams as well as top-scorer Oihan Sancet.

Mikel Jauregizar silenced the home fans and gave the visitors hope on the night with a stunning strike in the 31st minute.

For long periods of the match the visitors looked more dangerous but substitute Mason Mount settled the home supporters' nerves with 18 minutes to go.

The match totally changed complexion as Casemiro, Rasmus Hojlund and Mount again scored. It means United have kept alive their hopes of eking something out of a terrible season.

"I'm just worried about the next game, trying to not get any injuries for the final," United manager Ruben Amorim said. "If we don't win the final, it means nothing for us."

"We have to have a full squad against Tottenham, stay in the game and have a bit of luck and we have to be clinical," he added.

Winning Europe's second-tier club trophy crucially guarantees a place in the Champions League, which would boost United's chances of attracting top talent as Amorim attempts a monumental rebuild.

United were heavy favourites to complete the job on home turf but injury-hit Athletic nursed a grievance after defender Vivian was sent off in Spain.

They enjoyed the bulk of the early possession but struggled to fashion clear-cut chances and looked nervous when the visitors attacked.

Athletic midfielder Alex Berenguer had a good early opportunity after the home side failed to clear but his curling shot sailed over the bar as he aimed for the top corner.

The midfielder created another chance after a surging run midway through the half but fired wide of Andre Onana's post from just outside the area.

But the visitors broke the deadlock in sensational style after half an hour to give themselves hope when Jauregizar picked his spot from outside the box and curled past Onana.

The goal came after some sloppy work from United's defence. Harry Maguire played a ball across the box and Alvaro Djalo smashed a shot against Leny Yoro.

The ball fell to Jauregizar, who could not have hit the ball more sweetly.

United struggled for attacking rhythm but should have been level shortly before half-time.

The stadium held its breath as Alejandro Garnacho was put through by the lively Patrick Dorgu but his attempted dink over the goalkeeper went wide.

United offered little going forward in the early stages of the second half as Athletic made the running, forcing United to hack clear on multiple occasions.

Both teams made a triple change just after the hour mark. Shortly afterwards Unai Gomez headed the ball across the goal and it bounced just wide of the post.

Injury-hit Mount has been a peripheral figure in his two seasons at Old Trafford but produced a fine finish, swivelling and curling the ball into the far corner in the 72nd minute.

Casemiro scored a second with his head from a Bruno Fernandes cross as United's earlier nerves were completely forgotten.

Hojlund poked home in the 85th minute before Mount scored an outrageous second from near the halfway line after Athletic goalkeeper Julen Agirrezabala came out of his box and made a poor clearance.

Meanwhile, Tottenham kept alive their hopes of ending a 17-year trophy drought and saving Ange Postecoglou from the sack as they beat Bodo/Glimt 2-0.

After winning the semi-final first leg 3-1 last week, Postecoglou's troubled side weathered the storm in a second leg played in gale-force winds in Norway.

Dominic Solanke and Pedro Porro netted in the second half as Tottenham's 5-1 aggregate victory secured their place in the final in Bilbao on May 21.

Tottenham have already beaten United three times this season, winning 3-0 and 1-0 in the Premier League and 4-3 in the League Cup.

The north Londoners are aiming to win their first European trophy since the 1984 Uefa Cup and their first silverware in any competition since the League Cup in 2008.

Tottenham's last four finals have all ended in defeat, most notably the 2019 Champions League showpiece against Liverpool, while they were also beaten in the 2009, 2015 and 2021 League Cup finals.

Ending that dismal streak would fulfil Postecoglou's bold boast earlier this season that he always win a trophy in his second season.

We knew it was a difficult place to come. We're aware of the record they have here, the pitch. The lads handled it well. Excited, we're in a final," Postecoglou said. "You understand the context of what this football club has been trying to achieve for quite a while."

Despite languishing in 16th place in the Premier League, Europa League glory for Tottenham would also secure a place in next season's Champions League.

Whether that will be enough to spare the beleaguered Postecoglou from the sack is another matter.

The Australian has admitted the general perception outside Tottenham is he faces the sack regardless of the Europa League run because their domestic form has been so bad.

With three games left in the top-flight season, Tottenham are in danger of their worst finish since they were relegated in 1976-77.

United are just one place above Tottenham in the English top flight after an equally woeful campaign. (AFP)