Tim Howard produced an impressive personal display – but it was late frustration for the United States as Portugal grabbed an equaliser deep into stoppage time to earn a 2-2 draw in Manaus.
In what was another compelling World Cup group clash, the Americans looked on course to have produced a superb comeback win, one that would have seen them book a place in the last 16 of the tournament.
But Portugal, who were facing elimination, netted a last-gasp equaliser thanks to substitute Varela's bullet header.
Nani had given the hosts the lead on five minutes, only for Jurgen Klinsmann’s side to respond in the second half with an arrowing strike from Jermaine Jones and a close-range finish from Clint Dempsey.
Howard’s performance will attract plenty of praise, particularly a top-draw double save shortly before half-time when he pushed an effort from Nani onto the post before tipping the follow-up from Eder over the bar. It was a contribution that allowed the Americans to launch their spirited response in the second period.
The US, who beat Ghana 2-1 in their opening game, now move onto four points with one Group G game left to play against Germany on Thursday.
A draw or victory against Joachim Low’s team would see the US progress – but a German win would leave the door open for Ghana or Portugal to steal the final qualification position.