The United States must find their rhythm after falling out of sync in their 1-1 draw against the Netherlands, midfielder Andi Sullivan said, with everything on the line for their final match of the Women's World Cup group stage on Tuesday.

The four-time champions face a do-or-die meeting with debutantes Portugal in their last Group E game, where they must win or draw to avoid the humiliation of missing the knockout stage for the first time.

It is not the position the Americans hoped to be in as they pursue an unprecedented third consecutive title.

"(Portugal are) a strong team, going to be a tough game, we know what's on the line," Sullivan told reporters on Saturday. "We have shown a lot of pieces - it's just a matter of stringing all those pieces together and being very in sync."

A second-half goal from co-captain Lindsey Horan saved the US team from calamity as they scraped together a 1-1 draw against their 2019 final foes the Netherlands on Thursday in Wellington.

Despite a comfortable 3-0 opening win against Vietnam, the performance against the Netherlands showed the team has still not fully clicked, with some fans left confused as coach Vlatko Andonovski only made a single second-half substitution.

"We just weren't in sync and that happens and we were able to adjust it and respond. Hopefully we can do that earlier in the future," said Sullivan.

Even an outright win against Portugal would not necessarily be enough to take the top of the table, as the Netherlands, who also have one win under their belt, face Vietnam on Tuesday.

If the US team and the 2017 European Champions both win next week, the winner of Group E could come down to goal differential.

"We're going to need to play fast and score a lot of goals," said Sullivan, who is competing in her first World Cup.

"We also just want that for ourselves, regardless of the game and situation because we know our first two performances have been solid but we know we have more to give."