PARIS (Reuters) - The European Union "could and should" delay the implementation of certain bank capital rules if the U.S. drags its feet too long on fully implementing the Basel III rules, ECB policymaker Francois Villeroy de Galhau said on Wednesday.

President Emmanuel Macron and other French officials have long complained that U.S. banks are not applying the Basel III post-financial crisis capital rules, putting their European rivals at a competitive disadvantage.

Villeroy, who is head of the French central bank, said U.S. regulators had committed as recently as this month to "fully and faithfully" implement the Basel III international minimum bank capital rules.

"If, unfortunately, the delays and/or differences in content are too great, Europe could and should ... postpone the entry into force, or even adjust certain provisions, in particular those concerning market risks," Villeroy said.

An EU package of bank regulations adopted in December allows for a delay even if that would not be the best option, Villeroy said, speaking at a news conference of the ACPR French financial regulator, which he also heads.

The Basel III rules, which would apply to banks with over $100 billion in assets, would overhaul the way the biggest banks manage their capital, with knock-on implications for their lending and trading activities.

Macron called last month for a revision of how the EU applies the rules, saying "we cannot be the only economic zone in the world that applies them".

(Reporting by Leigh Thomas and Mathieu Rosemain, editing by Sriraj Kalluvila)