The Wales outside-half admits confidence is high among the Red Dragons following back-to-back victories over England and Italy.
But France are unbeaten as well following their success over Scotland and then against England at Twickenham and that has alarm bells ringing for Sweeney.
He said: "I really don't think we have seen the best of this French team yet. You never quite know what you're going to get with France but you know that if they switch on, then they can beat any team in the world. That's the difficulty about preparing to play them.
"They have won two from two yet they have still taken some criticism from their supporters and the media. They are proud rugby people and are bound to react to that."
Sweeney, who won his 19th cap as a replacement against Italy, has been restricted in his time on the pitch by Stephen Jones but insists he is pushing his rival all the way.
He said: "I'm not here to make up the numbers. I'm pushing as hard as I can to get into the starting team but it's hard to force your way in with Stephen and the rest of the boys playing so well at the moment. But that's great news for Wales."
Porthcawl recently received a WRU facilities grant and funding from Natwest RugbyForce in order to give their changing rooms a facelift. This came after receiving £10,000 in a WRU facilities grant last year to tarmac their car park. The improvements have already helped to make the club more accessible, not only for their own members and players but for the whole community.
The Welsh Rugby Union has launched a new, accredited Safeguarding and Protecting Children course - funded by the WRU and delivered in partnership with Sport Wales and the NSPCC - fo rugby club volunteers around Wales.
The SWALEC semi-final draws threw up some mouth-watering clashes in the Cup, Plate and Bowl as the 12 teams aim for the Millennium Stadium Finals Day. All the semi-finals are to be played on the weekend of April 12.
Welsh whistler Rhys Thomas continues to scale the heights of the game as he prepares to be an official in this weekend's Hong Kong Sevens tournament, undoubtedly the showpiece event on the World Series calendar.
Wales International Ian Evans and Wales and Lions legend Scott Quinnell swapped rugby balls for paint pots at Tonna during the RBS 6 Nations. They surprised club players with a special clubhouse makeover to launch NatWest RugbyForce 2014 - a programme developed in partnership with the WRU to make rugby clubs stronger businesses by improving and renovating their facilities with the support of volunteers and the local community.
Fresh from claiming the Bowl honours in Tokyo last Sunday, the Wales Sevens squad have settled into their routine as they prepare for this weekend's Hong Kong tournament where Iolo Evans is aiming high, as WRU TV's Graeme Gillespie discovers.
The Welsh Rugby Union has recently teamed up with Prostate Cymru to help the charity launch its latest campaign to raise awareness of the disease. Members of the Wales squad helped produce a short video and promotional material for the campaign titled 'The Best Defence - is to know the FACTS'.