France fly-half Romain Ntamack says Ireland are "comfortably favourites" for Saturday's predicted Six Nations title decider in Dublin.

Ireland opened their Six Nations with a dominant 34-10 win in Wales with France tested in Italy before winning 29-24.

"They are world number one. It's not for nothing. They are comfortably favourites," said Ntamack, 23.

"There's no debate. They showed and proved that in round one against Wales.

"They're good in all areas. They have very few weaknesses, if any. It's going to be an arm wrestle for 80 minutes."

World Cup hosts fully focusing on Six Nations

This year's Six Nations has the shadow of the France-hosted Rugby World Cup looming over it.

France kick off the tournament against three-time winners New Zealand in Paris on 8 September but the Toulouse star insists Les Blues are fully focusing on the Six Nations for now.

"First things first, we'll be happy to win on Saturday. It would mean that we're still in line for a second Grand Slam. It's really the objective," he added.

"Beyond impressing, beyond thinking about the World Cup, if we want to defend our title and write history, it comes with a win in Ireland."

At the Stadio Olimpico last Sunday, Ntamack set up two tries for team-mates after a November campaign where he was not at his brilliant best despite French wins over World Cup holders South Africa, Australia and Japan.

"Those things happen. I know what I do well, what I do less well," said Ntamack.

"It didn't stop me sleeping. I'm happy to be back to my best."

Nine of Ireland's starting team from last weekend play for Leinster, who have won the Heineken Champions Cup on four occasions, which is only one behind the tournament record holders that Ntamack plays for.

"They have played together for a while: 90% of them come from Leinster, they're together for the whole year," added the France fly-half.

"They know each other inside out. They're great players who are used to playing big games."

In Rome, Ntamack and Toulouse team-mate Antoine Dupont reached a France record of 22 internationals together as a half-back partnership.

In Dublin, they are likely to face 110-time capped fly-half Johnny Sexton, who is now 37, and his fellow Test centurion Conor Murray.

"They are players that we admire, who have lasted, despite their age, they're still performing well," Ntamack said.

"It shows their efficiency in the Ireland shirt. It's inspiring but it stops there, they are our opponents. Even if we respect them, we will try and beat them."