Charles Boehm is covering the USMNT and the World Cup for Gothamist from Brazil for the duration of the tournament. He has covered MLS and the American soccer scene since 2004, contributing to MLSSoccer.com, The Soccer Wire, and USSoccerPlayers.com.

MANAUS, Brazil - The tropical sun burns hot here on the shores of the Amazon River, and from disease-carrying mosquitoes to toothy caimans and piranha, a bevy of beasts great and small can haunt visitors' dreams—especially if the side effects to their anti-malarial medications kick in.

The U.S. national team have journeyed to this bustling riverside port to face Portugal and Cristiano Ronaldo, the planet's most menacing creature on a professional soccer field.

As they have all week long, on Saturday the media peppered U.S. head coach Jurgen Klinsmann and his players—on this occasion, veterans Tim Howard and Jermaine Jones— with questions about the tall task of facing down the FIFA World Player of the Year and his teammates at the beautiful but controversial Arena Amazonia in another crucial World Cup match on Sunday evening (6 p.m. ET, broadcast on ESPN/Univision).

“He's strong, physically he's a fast runner, he's the best in the world with the ball at this feet. Good striker, left and right foot. Dominant in the air. And the list goes on and on,” said Howard of Ronaldo. “And that's why he's the best player in the world. We're going to try to do our best to bottle him up. It's not been done in four or five years, but we'll see what we can do.

“We feel like we have a game plan in place. If we can execute that, we give ourselves a chance.”

With Group G's other two teams, Ghana and Germany, drawing 2-2 on Saturday afternoon, the U.S. now know that a win over Portugal will move them to first place in the group and clinch a berth in the tournament's knockout stages with one group game still to play. That would represent a delirious success, given the generally bearish outlook on their chances since the World Cup draw took place back in December.

But despite their 4-0 thumping at the hands of Germany last weekend, Portugal remain a daunting proposition, even with several starters injured or suspended and Ronaldo himself reported to be less than 100 percent due to a chronic knee problem. Coach Paulo Bento's side are ranked fourth overall in the current FIFA World Rankings and boast a talented roster hailing from many of Europe's biggest clubs.

“There is a lot of admiration for Cristiano and for the players that play overseas, that play in the big clubs, and play [UEFA] Champions League and all that stuff,” Klinsmann replied when asked by a Portuguese journalist if Ronaldo was more famous in the United States than he is, an idea he cheerfully agreed with. “But this is now the moment where you can prove yourself, this is the moment where you can step up and play those guys, and put them in place. So we want to put Cristiano and his team in place.

“We respect them highly, which we always do, but we are ready to get this started.”

The heat and humidity of this industrial city, one of the most remote metropolises on earth, has been a major point of contention during the World Cup. To further complicate matters, heavy rains have soaked the playing surface at Arena Amazonia and with more thunderstorms in the forecast, conditions could get sloppy on Sunday.

But the ever-sunny Klinsmann wasn't interested in talking about those worries.

“Obviously, we are aware of the conditions and the climate and everything,” he said. “I think we are very well prepared for this climate here. We have similar climates to play in in CONCACAF in Central America, or even if you go through Florida and you play in Miami, it's very similar to what you experience here. I think we are very well prepared for tomorrow.”

The venue itself offers a fascinating backdrop. A brand-new, 40,549-seat facility with a soaring roof structure inspired by the region's traditional woven baskets, Arena Amazonia is beautiful, but its impracticality and its price tag have made it something of a poster child for Brazilians' frustrations about this World Cup.

It cost nearly $300 million to build and is being used for only four matches. And with Manaus' largest professional club, Nacional FC, playing in the lower reaches of Brazil's league system, it's unlikely to ever be put to maximum use again once this summer's tourists have gone home.

Local government officials hope to stage high-profile matches between more popular clubs from other cities and FIFA's official venue page says the arena is “an important legacy for the region” that will host “concerts and cultural events.” Yet it's hard to escape the conclusion that this will be Brazil 2014's biggest white elephant.

Perhaps it's appropriate, then, that the U.S. will go big-game hunting here on Sunday.

By Charles Boehm