Efforts to limit the amount of refugees seeking the shores of Europe are working, Nato secretary general Jens Stoltenberg said.
Speaking in Ankara, Mr Stoltenberg said the collective effort is "making a difference" and that the number of people crossing the Aegean Sea is "significantly down".
Under an EU-Turkey deal signed last month, migrants arriving on Greek islands from the Turkish coast from March 20 onwards face deportation to Turkey unless they successfully apply for asylum in Greece.
Greece has seen fewer than 70 arrivals per day in the past 10 days, down from nearly 1,500 arrivals per day before the deal was struck, according to the International Organisation for Migration (IOM).
Nato began patrolling the Aegean Sea in February to help stop the smuggling of migrants.
Mr Stoltenberg said Turkey, based on information that Nato provides, is "taking action to help break the business model of traffickers".
But he warned the fight against trafficking requires "flexibility" as smugglers can "shift their routes rapidly".
The migrant crisis demonstrates how urgent it is to find a solution to the Syrian conflict, Mr Stoltenberg added.
Turkey, which borders Syria, is home to 2.7 million Syrian refugees.