Johnny Sexton says Ireland cannot be considered the world's best team until they have won the Rugby World Cup.

But the Ireland captain, 37, feels his side must emulate Saturday's opponents South Africa and lift the Webb Ellis Cup to truly earn the number one tag.

"Honestly, it's not something we really talk about much. It's not a goal to be number one in the world," he said.

"That might sound stupid. In some sports it is - golf, tennis - but in rugby the rankings matter once and it's three years out from the World Cup (needing to be in the top eight for the pool draw), which doesn't make that much sense either.

"We don't speak about being number one. To be number one in the world, you need to win the World Cup, that's where the goals are.

"Obviously you want to be the best in Europe, you want to win the Six Nations, those are our goals; it's nothing to do with being number one and I don't think many teams read too much into it.

"I know the other teams will probably refer to us now, trying to put pressure on it, but we don't speak about it."

'How are we going to mess up Ireland?'

Ireland begin their autumn Test series against reigning world champions South Africa in Dublin on Saturday and then face Fiji and Australia.

The Springboks' visit to Aviva Stadium - where they lost 38-3 in 2017 - will double up as a dress rehearsal for the sides' World Cup pool stage match in Paris next year.

And while Sexton dismissed Ireland's status as the world's top-ranked team, he says their series victory in New Zealand gives Andy Farrell's side a target on their back.

"We have to give them the respect that they absolutely deserve," Sexton said of three-time world champions South Africa.

"They're the best team in the world in terms of they're world champions. They're a top-class team.

"They've obviously won the World Cup, they beat the (British and Irish) Lions (in 2021) and had some big results over the last few years, so in terms of testing ourselves it's huge.

"We need to bring our game and make sure we do it even better because when you have a couple of results like we did in the summer, teams start to properly look at you and go, 'how are we going to mess up this Ireland team? How are we going to combat this?'.

"We've got to do it better and we've got to evolve a little bit and make sure we bring something new to the table."