Sweden coach Erik Hamren has admitted that his side were below par during Friday's defeat to Portugal in the first leg of their World Cup qualifying playoff.

Cristiano Ronaldo found the net late on in Lisbon to give the hosts a narrow 1-0 advantage heading into next week's second leg in Stockholm.

"Portugal pushed more in the second half and we were forced to play too many balls in the air," Hamren is quoted as saying by Goal.com.

"The goal we conceded was a bit sloppy. I'm always disappointed when we lose, but I would have been really happy with the draw.

"After this we must win the next game at all costs. We will do everything we can to win."

Sweden welcome Portugal to the Friends Arena on Tuesday.