Wales slip to fifth in the International Rugby Board world rankings after their defeat to France last week, but the reigning RBS 6 Nations champions remain the highest-ranked European nation.
Warren Gatland's side swap places with Argentina, who climb to fourth.
Ireland, the only side who can still complete the Grand Slam, remain sixth after their slender 14-13 victory over England.
Declan Kidney's side would overhaul Wales in the IRB rankings if they secured the elusive clean sweep, which would mean their first home championship win since 1985, and their first Grand Slam in 61 years.
Martin Johnson's England have slipped to their lowest-ever IRB ranking, eighth, after that defeat at Croke Park.
France are the beneficiaries, moving back up one place to seventh courtesy of their entertaining win at the Stade de France.
England still have a cushion of three and a half points over Scotland, who remain ninth following a first win in this year's RBS 6 Nations - 26-6 against Italy - a little further away from Fiji in 10th.
The Azzurri's defeat at Murrayfield drops them a further one spot back to 12th, behind Samoa.
The southern hemisphere nations hang on to the top three positions unchanged. New Zealand remain top, with South Africa second and Australia third.