"There should be a zero doubt policy about our commitment," Füle told a joint news conference with Turkish ministers in Istanbul. "We have a very clear mandate from member states."
Turkey is irked by the slow progress in formal negotiations begun five years ago.
"We will be looking at ways we can speed up the accession process," Füle said. "No one is happy at the current speed."
EU foreign affairs chief Catherine Ashton and Füle met Turkey's Foreign Minister Ahmet Davutoğlu and EU Affairs Minister Egemen Bağış for a first set of talks under a new political dialogue process meant to bring the two sides closer together.
Turks suspect some EU states of foot-dragging due to their reluctance to let in a Muslim nation, whose membership would mean the EU losing a buffer between itself and the Middle East.
Out of 35 chapters - subject areas for negotiation prior to EU entry - Turkey has completed one and opened 13 others, leaving 21 to go (see EurActiv LinksDossier on EU-Turkey relations).
All but three are blocked, mainly due to an impasse over the divided island of Cyprus, an EU member whose government has obstructed Turkey's progress over Ankara's support for Turkish Cypriots, who broke away from their Greek counterparts.
Turkey is backing reunification efforts, and wants the EU to lift its embargo in the Turkish north of the island, while the EU expects Turkey to open its ports and airports to traffic from Cyprus.
Füle gave his backing to the government's proposed package of constitutional changes that Turks will vote upon in a referendum on 12 September.
He said the package met the EU's expectations on a number of issues and described it as a positive step in the framework of Turkey's candidacy for membership.
Most of the proposed changes are uncontroversial, but the government's plans to change the way senior judges are appointed has triggered a debate over whether it contravenes the principle of separation of powers.
Critics of Prime Minister Tayyip Erdoğan's AK Party say it is an attempt to take control of the judiciary, which is regarded as the strongest bastion of Turkey's secularists.
The AK Party's critics suspect the party of harbouring a secret agenda to roll back secularist ways established by the modern republic's founder, Mustapha Kemal Atatürk.
The party denies having any such plans, and sees itself as a Muslim version of socially conservative Christian Democrat parties in Europe.
(EurActiv with Reuters.)