* Two Dos Santos goals disallowed in first half
* Peralta strike wins match
* Eto'o fails to fire for Cameroon
By Nick Mulvenney
NATAL, Brazil, June 13 (Reuters) - Mexico kept their eyes firmly on the prize through a Natal rainstorm and two controversially disallowed first-half goals to run out deserved 1-0 winners over Cameroon in their World Cup opener on Friday.
Oribe Peralta's 61st minute strike was just reward for the attacking intent they showed throughout and turned Mexican fury at the two Giovani dos Santos efforts being rubbed out into unbridled joy.
With the chaos of their qualifying campaign now a fading memory, Mexico and their thousands of fans move on to their meeting with hosts Brazil charged with confidence that they can finish above Cameroon and Croatia and qualify from Group A.
"The team surpassed my expectations on the pitch," coach Miguel Herrera told reporters.
"We had a lot of opportunities to score goals and we ran hard. I'm thrilled because the team worked collectively and left everything on the pitch."
For Cameroon, branded traitors by critics back home after the player strike over bonuses that delayed their arrival in Brazil, a fifth successive World Cup defeat means they face an uphill task in avoiding another first round exit.
Coach Volker Finke had packed his midfield in a failed attempt to stifle the effervescent Mexicans and his lone striker Samuel Eto'o failed to make the most of his few opportunities.
After a week of mostly sunny weather befitting a beachside resort city, the skies opened a couple of hours before kickoff to leave a rain-saturated pitch and the largely Mexican crowd shrouded in plastic macs.
Man of the Match dos Santos was a livewire threat from the start and he first found the net with a neat volley after 11 minutes but was called back despite appearing to be in line with the defenders.
Cameroon could have taken the lead after 21 minutes when fullback Benoit Assou-Ekotto beat two defenders and found Eto'o in the box but the team captain was able only hit the outside of the post.
If the decision to deny dos Santos a first goal could charitably be called a marginal call, the second after half an hour was a clear error.
A corner swung in from the left was flicked on by one Cameroon defender and, as another raced off the line, dos Santos managed to turn back and head the ball into the net.
The crowd howled their disapproval and Herrera was apoplectic on the touchline as the match headed for the break goalless.
"At no time did we think about the referee during halftime," said Herrera.
"What we told the team was that concentration was essential. Never at any time did the team lose concentration. The attitude was wonderful today. The team showed they were mentally strong."
As the rain continued to lash down, striker Peralta almost broke the deadlock three minutes after the break when Dos Santos's flick played him through on goal only for Cameroon goalkeeper Charles Itandje to block his shot with his legs.
Cameroon's Assou-Ekotto had a free kick deflected off the Mexico wall and just wide after 58 minutes but the game did not have to wait much longer for its first goal.
Dos Santos was released through the middle of the Cameroon defence and when Itandje managed to stop his low drive, Peralta was on hand to steer the ball into the empty net.
The Africans continued to threaten from set pieces, however, and Mexico goalkeeper Guillermo Ochoa was forced to leap high to his right to prevent Benjamin Moukandjo equalising with a header in stoppage time.
Cameroon have now won just one World Cup match since becoming the first African team to reach the quarter-finals in 1990 and Finke admitted he had his work cut out before the match against Croatia in Manuas on June 18.
"We need to motivate the players again," he said. "The next game is a decisive game. If we want to remain in this World Cup it is obvious we need to get a result in the next match." (Editing by Justin Palmer)