Portugal squeezed into the knock-out stage with a 1-1 draw against Iran and will face one of the form sides in the tournament.
Uruguay are one of only two sides to win all three of their group games so far, and they have added some midfield guile to the physical style for which they are known and feared.
"There's no doubt that Uruguay have excellent players. They have an excellent team. They were world champions twice," Soares told reporters.
"It's an excellent team but we also have our weapons. We are going to have time prepare for this encounter in the best way possible. Needless to say, we have our qualities and we really believe in them."
"We're European champions and we've already shown many times what quality we have, and we're going to continue doing that," he added.
"All our opponents have big players and some smaller players. In football it's irrelevant. We have to attack the ball, and treat every ball as dangerous, always be aware. That's how we're going to face every instance of the game against Uruguay."
Uruguay have one of the best recent records of all 32 World Cup sides, having won all six of their games this year, conceding precisely zero goals.
But Soares underlined that Portugal were taking a difficult tournament one game at a time and said from now on every match is decisive.
"This has proved to be difficult for all the teams involved, it's a very competitive World Cup. Our main goal of course was to qualify and we've done that. Now we are preparing for the last 16. That's very tough, because every game from now on is a final. We're going to face them that way."
(Reporting by Andrew Downie; Editing by Hugh Lawson)
