In their most difficult test thus far, the defending champions came through unscathed, securing a comfortable 2-0 victory against Sweden to make it three wins from three in France with no goals conceded.

For athleticism, for speed, for attacking prowess the US is without equal at this Women's World Cup. Indeed, no team has ever scored more in the group stages than the 18 goals netted by Jill Ellis' side.

Sterner tests will come, but probably not until the quarterfinals when France, if the last-16 ties go as predicted, will likely be the opponent for what would be a mouthwatering contest in Paris.

From the moment Lindsey Horan struck in the third minute in Le Havre for the quickest goal of the tournament the result was never really in doubt. That a Jonna Andersson own goal was the only addition to the scoreline will probably be an irritation to a team from which much is expected.

The US wasn't without weakness, there were occasions when the defense erred -- Kosovare Asllani glided through on goal far too easily in the first half -- but it concludes the group stages atop Group F and as justified favorite for a fourth title.

Ellis' biggest worry is likely to be Alex Morgan's half-time departure after a heavy challenge in the first half. The coach later said that substituting her star striker was a matter of being "smart about things."

Horan (C) scores the opening goal against Sweden.

Three years ago, Sweden knocked out the US at the quarterfinal stage of the Rio Olympics, inflicting on the US its worst showing in a major tournament.

Ellis denied that the loss in Rio had played on her mind in the build up to this match. "I don't have a rear-view mirror," she told reporters after the match. "It's all about what's in front of me. I didn't give that game a second thought."

Since that defeat in 2016 Ellis has tinkered with rather than overhauled the team's style of play and so far in France her side has impressed, advancing into the last 16 with a 100% record and a goal difference of +18. Germany is the only other country to progress to the knockout stages with a blemish-free defensive record.

Speaking after her ninth win as US coach in 10 World Cup matches, Ellis added: "We wanted to talk about continuing to build momentum, but we've got some things to work on to make sure we're better and sharper for the next game.

"When you come out of the group stages a lot of what you talk about is mentality and being healthy and I think they're in a really good place.

"To have the players in a good place with self belief makes my job easier because they're certainly highly motivated and hungry."

Heath celebrates with Kelley O'Hara after the US' second goal.

Ellis opted for mostly the same personnel which started the record 13-0 opening victory over Thailand. Midfielder Julie Ertz -- a player who kept a photo of the Sweden defeat as a screensaver on her phone as a way of using failure to fuel the fire -- was the only absentee through injury.

With progress also assured Sweden made seven changes to the team which beat Thailand in its last outing. Four players were given their World Cup debuts for a formidable baptism on the big stage.

Coach Peter Gerhardsson said he made the selection with an eye on the knockout stages.

"We know we have a knockout match on Monday and that's the most important game," he told reporters.

"We talked more than ever about the starting XI both with the medical team, coaches, players etc. When we looked at the game plan, we didn't think in advance that it was important to end up first or second."

With Sweden not at its strongest, it was a straightforward night for the three-time champions.

The US had 18 attempts on goal, though only four of which were on target, and enjoyed 58% of the possession. Indeed, Ellis' side completed more than double the amount of passes than its opponent.

But Ellis denied that the Swedes had made it easy. "You're not giving enough credit to the opponent we played," she said. Sweden is a good opponent to play in a group stage game, as it has been in tournaments past."

The US and Sweden are familiar foes. No other teams have played each other on more occasions at Women's World Cups so Sweden should have been alert to the danger the defending champions pose at set pieces.

But when Megan Rapinoe swung in a low corner, Sweden's defenders allowed the ball to fall into the path of Horan, leaving the impressive midfielder with a simple strike a few yards from goal. Even Thailand had held firm for longer.

Despite the US' monopoly of possession and territory, it wasn't until the 50th minute that the second breakthrough came.

Rapinoe was again the creator, finding the effervescent Heath who aimed at goal from an acute angle, forcing Andersson to direct the ball into her own net. Should the goal have been disallowed? Substitute Carli Lloyd appeared offside in the build up, but VAR deemed that the striker was not interfering with play.

Lloyd should have scored a third in the dying minutes, but the striker drew a fine save from Hedvig Lindahl.

Sweden will play Canada next on Monday, while the US will now turn its attention to a last-16 match against Spain, a team which is competing in the knockout stages for the first time and one which the defending champions defeated 1-0 in a friendly in January.

"Spain's a great side," said Ellis

"It was really purposeful why we wanted to play them earlier in the year. It was great to get them on the schedule and experience that in their home country.

"Any team that gets out of the group and is in this position you 100% respect and obviously we need to have very good preparation and performance to do very well against them."