Portugal were held to a disappointing 1-1 draw in their opening group match against DR Congo last week but the coach has shut down any talk of disharmony in his squad as debate continues to rage about the involvement of legendary forward Cristiano Ronaldo.
Martinez said: "We're more united, we're stronger.
"We're playing a World Cup, of course there's a lot of noise, a lot of tension, it's part of the game. Our focus is on the team.
"We're more united than before we arrived. There's no tension."
Ronaldo, 41, has failed to score in his last 10 major tournament games but Martinez once again came to the defence of his captain.
The coach said: "He's probably the biggest example of how to recover, how to train. But that doesn't take away the feeling of frustration we all have, as a team."
Meanwhile, Portugal full-back Joao Cancelo has urged the team to utilise their attacking talent when they take on Uzbekistan in Houston on Tuesday (23.06.26).
He said: "We didn't create chances (against DR Congo), and that isn't normal in a team like ours. We have high-quality players, among the best in the world, and we have to show that on the pitch.
"[Against Uzbekistan], only winning counts. We don't have any margin for error."
Cancelo also suggested that Ronaldo and Brazil forward Neymar don't deserve the criticism they have received at this World Cup.
He said: "I don't think Neymar or Cristiano need to prove anything to anyone.
"Their talent and what they've achieved in football speak for themselves. All that talk is just for show. Both Cristiano and Neymar know who they are and what they represent for their countries."
