Winning the inaugural SheBelieves Cup would be as "big an achievement" as claiming bronze at last summer's World Cup, says England boss Mark Sampson.
The Lionesses take on the world's top three sides - USA, Germany and France - in a new four-team competition.
"This is by far and away not a friendly tournament," he said. "It's probably one of our biggest challenges ever."
England kick off against the hosts in Tampa on Thursday, in a game live on BBC One (Friday, 00:45 GMT).
The US won last year's World Cup, beating Japan in the final.
England were beaten by Japan in the semi-finals but beat Germany to finish third, the second best World Cup performance by an England team following the 1966 win by the men's side.
"The World Cup was a magnificent achievement," added Sampson. "But if we were to come away with this cup, you could argue that it's as big as an achievement from a football perspective."
England's games will be shown live by the BBC:
- 3 March v USA in Tampa, Florida. BBC One (00:45 GMT)
- 6 March v Germany in Nashville, Tennessee. Red Button and BBC Sport website (22:45)
- 9 March v France in Boca Raton, Florida. Red Button and BBC Sport website (22:00)
With England currently fifth in the Fifa rankings, Sampson admits his players will start this week's tournament as clear underdogs.
"The challenge for us is to show that we belong and that's our focus," said the Welshman.
"We are the underdogs, we're the bookies' favourite to finish bottom and the wooden spoon's ready with England's name on it.
"Most importantly for me is that everyone in that changing room believes that England are going to win this tournament.
"Back home, we've got to prove a few doubters wrong. We know that. But if we were to win this tournament, it would have a big impact."
England v 'Big Three':
- The Lionesses have beaten USA once in the last 23 years
- England's victory in the 3rd/4th placed play-off at last summer's World Cup was their first win over Germany in 31 years
- England have not beaten France since 1974
Sampson has picked 19 of the 23 players from his World Cup squad for the tournament, with Gemma Davison, Isobel Christian, Gilly Flaherty and Demi Stoked also selected.
However, he warned his experienced side that they would have to be at their very best is they are to overcome their opposition.
"This is England going up against the three best teams in the world and in the world's best team's backyard," he said.
"We've got a real clear objective... we're here to win it, to be as difficult as we can for our opponents and to make the games a living nightmare for them. We believe that if we get things right, we can cause some upsets".