“Coming back to the market is important, but I would say it is an important error. There is always a risk that things do not work out as planned and that a fourth bail-out will be needed,” Gros told CNBC.

A source familiar with the situation, who didn’t want to be named because of the sensitivity of the issue, told CNBC that the timing of Greece’s return to the bond markets is not yet know.

“We don’t know for sure if Greece will try to tap the markets next week or wait until the fall,” the source said. Greek government officials have signaled that they aren’t ready to tap the markets next week, but Greek bankers seem to be in contact with the Greek debt issuance agency, the source said.

On Wednesday, the European Commission said Greece’s fiscal position has improved and it had decided to lift the risk of disciplinary procedures against Athens over its excessive deficit.

Pierre Moscovici, commissioner for economic affairs, told reporters that the chances of seeing Greece returning to the market again were becoming “more credible”.