LONDON, Jan 12 (Reuters) - Arsenal boss Mikel Arteta said he was astounded his side could not finish off 10-man Manchester United ( MANU ) in their FA Cup third round clash on Sunday, after they were dumped out on penalties having drawn 1-1 after extra time.

The hosts came from behind to level, Gabriel cancelling out Bruno Fernandes' opener after United's Diogo Dalot was sent off, and could have taken the lead through a controversial penalty.

But captain Martin Odegaard's spot kick was saved by Altay Bayindir, who produced the only save of the shootout from Kai Havertz to send United through to the fourth round.

Arsenal had multiple chances to score a winner at 1-1, with Havertz guilty of missing a relatively simple chance inside the last 10 minutes of normal time, and Arteta could not quite believe his team were on the wrong side of the result.

"Incredible how you don't win the game," he told reporters. "The dominance, the superiority in relation to the opposition and everything that we did to try to win the game and that's it.

"We didn't get what we deserved clearly, but there is an element that is about putting the ball in the back of the net.

"We did it once and with the amount of situations, chances, penalties that we had we didn't (again). We go home extremely sad but I cannot be prouder of my players."

Arsenal came into Sunday's match unbeaten in 10 Premier League games and having trimmed Liverpool's lead to six points, albeit having played a game more.

But Sunday's FA Cup exit, following a 2-0 home defeat by Newcastle United in the first leg of their League Cup semi-final, narrows the Gunners' prospects of silverware this season.

They next welcome local rivals Tottenham Hotspur to the Emirates Stadium on Wednesday, but Arteta played down any additional pressure after two straight cup losses and insisted he was focused on the quality of their performances.

Gabriel Jesus was carried off the field on a stretcher in visible discomfort in the first half on Sunday and Arteta said he feared the Brazil forward could face a prolonged spell on the sidelines.

"Big worry, that's my feeling," Arteta said. "He had to come off on a stretcher with a lot of pain, touching his knee and he's not looking good."