Like a theater audience demanding to be entertained, French football fans can be a fickle lot.

The team will be keen that tradition doesn't re-emerge on Sunday when it takes on Iceland in the quarterfinals of the European Championship. Iceland, after all, is extremely popular among neutrals after its 2-1 victory over England in the round of 16.

Les Bleus have often endured a fractious relationship with their fans. Relations are better, but still precarious.

Last weekend in Lyon, the players were jeered off at halftime against Ireland, when trailing 1-0. In the group game against Albania in Marseille, the vocal frustration was evident until Antoine Griezmann's 90th-minute goal.

Any frayed nerves among the French contingent at the Stade de France this Sunday will surely contrast with those of Iceland's devoted fans, who will be shouting their traditional Viking chant and cranking up the pressure on France's players.

Ideally for France, a quick goal or two would help settle nerves.

That France has failed to score in the first half in this tournament may not be just a coincidence. Players start games nervously as if trying to avoid mistakes. Chances are snatched at, the body language is tense and cagey, the fans rarely indulgent.

"I think we should be a bit more supportive," France fan Ahmed Kchikech told The Associated Press after a public team training session on Wednesday. "We're fed up with things only happening in the second half ... French fans are like this. We don't forgive (the players) the slightest mistake."

Kchikech said he feels envious at the way Ireland and Iceland supported their teams at this tournament, with prolonged chants and heart-warming songs.

"It's magnificent ... but that's not the French way," he said.

Over the years, games have often mapped out the same way at the national stadium.

A flag-waving rendition of La Marseillaise — the national anthem — followed by some hearty early encouragement and then a tense, watchful silence. If France fails to impress, jeers and boos ring out from the stands.

The French players have often spoken about being upset during games when the fans turn. Speaking after a 2-0 defeat to Argentina in 2009, left back Patrice Evra berated France fans for sarcastically supporting Argentina.

"All the matches we play in France feel like they're away from home," Evra said.

There's little doubt that the French side has not always helped itself — notably at the 2010 World Cup in South Africa when the players went on strike.

Things have improved, especially in November 2013 when France overturned a 2-0 first-leg deficit against Ukraine to win 3-0 at the Stade de France and qualify for the World Cup.

Since coach Didier Deschamps took charge after Euro 2012, he has opened up more training sessions to the public.

On Wednesday, some 500 fans attended a training session at France's base at leafy Clairefontaine on the outskirts of Paris. Deschamps and the players happily signed autographs and chatted with fans before training.

On Sunday, they will hope they remain supportive.