In the first round of the FIFA World Cup, there are groups of 4 teams, which play each other in order to qualify to the second round. It is generally said that if a team wins its two first matches, it is assured its qualification. Is this true?

Some notes for non-soccer fans... The two top teams (points-wise, or after tie-breaking rules are applied) in each group qualify for the next round. Each team plays the three others. A win gives three points; a draw, one, and a loss, zero.