Turkey and the European Union faced off Thursday over a proposed deal to let Turks travel to Europe without visas — a crucial carrot the bloc has been dangling in order to get Turkey to halt the torrent of migrants flowing from its shores to EU member Greece.

But with each side insisting the other give ground over an EU demand that Ankara more sharply define its anti-terror laws before it gets the visa waiver, a prolonged waiting game appeared to be shaping up.

The issue of visa-free travel to Europe for Turks could ultimately derail an EU-Turkey accord under which Ankara agreed to stop migrants from leaving for Europe and take back those who do arrive. For the moment, though, the migration deal that was sealed in mid-March remains on track.

The waiver is an incentive, along with up to 6 billion euros ($6.8 billion) and fast-track EU membership talks, for Turkey to stop the migrant flow. But now the two sides appear in danger of missing the planned visa waiver date of June 30.

Turkey has already fulfilled most of the 72 conditions to secure the waiver but one has emerged as a major obstacle. President Recep Tayyip Erdogan and other officials say Ankara won't narrow its definition of "terrorist" and "terrorist act." EU nations worry that the current laws can be used to target journalists and political dissenters.

Erdogan has warned that the entire migrant deal could collapse if the Europeans renege on their pledges. There still appears to be some maneuvering room — Erdogan said this week that Turkey would go its own way if the visa waiver isn't introduced by October.