World champion Japan may have missed out on a third consecutive win over the United States on Sunday, but coach Norio Sasaki insists the 1-1 draw in the opening match of the Kirin Challenge Cup has given him further cause for optimism ahead of the London Olympics.

Defender Yukari Kinga fired Japan, missing star midfielder Homare Sawa, into a 32nd-minute lead in Sendai, and the hosts looked to be a good bet to add to their victories over the Americans at the 2011 World Cup final and last month's Algarve Cup.

But late pressure from the visitors paid off as in-form Alex Morgan leveled in the 72nd minute with a goal that looked set to be disallowed after a linesman had initially flagged for offside.