Fernando Alonso finds it "painful" to have lost so many Formula 1 points in recent races after being forced to retire from Sunday's United States Grand Prix due to an engine problem.

Alonso set his sights on ending a points drought dating back to the Hungarian Grand Prix in July on Sunday in Austin, lining up seventh on the grid and holding his position through the early part of the race.

After completing his one planned pit stop, Alonso remained in contention for points, only to slow when an engine issue emerged on his Honda power unit that forced McLaren to retire the Spaniard.

"Today I think we really deserved to collect some points. We did a good qualifying, a good race, and made a good start, but with no reward," Alonso said.

"From our side I think it was an amazing performance. On the straight I lost power – I felt some vibrations in the engine and some really weird things were going on.

"It’s such a pity. In the last few races we have lost so many points – possibly 15 or 20 – which probably could have helped our position in the championship for myself and also the team.

"It’s painful, especially because today we were seventh on merit and we had fought for that."

Alonso remains determined to see out the season as well as possible in order to do the McLaren team justice after a tough campaign that has seen it finish a race no higher than sixth.

“There are only three races remaining and we really want to do well, because the boys in the garage work really hard day and night to prepare the cars properly," Alonso said.

"Even this morning they had to change Stoffel [Vandoorne]’s engine and both crews were working together on that, then they prepared for the race and performed some perfect pitstops.

“Today really was a missed opportunity.”