On a visit to Bucharest, Emmanuel Macron urged Romania to take part in discussions about reforming the controversial passport-free movement across most of the bloc.
The Schengen zone, which is an area of free movement between country borders, has been blamed for migrant chaos in Europe and a heightened terrorist threat.
The French president said: “You’ve been having the right to request entry into the Schengen area for years now, and you have recalled this, and I know how important this is for you.
“I have no ideology in this respect, I am totally open to this subject.
“But I have to be honest, the Europe of the Schengen area is not working well and, of course, we can’t be happy about it.”
The Romanian President Klaus Iohannis said that Romania was “already acting de facto as a responsible state of the Schengen area, taking part in the joint efforts to strengthen the Union’s external borders”.
He added: “Romania’s accession will strengthen the security of the Schengen area and will send a strong signal in support of the European construction.
“Romania is today, 10 years after becoming a member, a mature member state with a very powerful pro-European profile, that wants to be a re-founding member of the European Union.”
Mr Macron arrived in Bucharest on Thursday, August 24, for a one-day visit.
His controversial comments are the latest in the one-time EU golden boy’s attacks on the bloc.
EU chief’s applauded his election earlier this year but the French president has since urged for reforms of the union.
The Schengen agreement was signed into EU law in the 1997 Treaty of Amsterdam.
There are currently 26 countries in the Schengen area: 22 of these are EU members and four are non-EU member states – Switzerland, Liechtenstein, Iceland and Norway.
The UK and the Republic of Ireland, however, have both opted out of the internal border policy.
Jean Claude Juncker, the European Commission president, has said the Schengen system is non-negotiable, irreversible, and the EU’s greatest achievement
However, the former leader of Ukip, Nigel Farage said: “Schengen has now hit the buffers of the real world and is falling apart.”