EU leaders are to hold emergency talks in Brussels on the Mediterranean migrant crisis.
The Greek government did not say what Tsipras and Merkel would discuss at their meeting in the Belgian capital.
Tsipras' cash-strapped leftist government is under pressure from fellow eurozone members and the IMF to present details of reforms needed to unlock some 7.2 billion euros ($7.8 billion) in bailout funds.
On Friday, eurozone finance ministers will meet in Latvia's capital Riga to discuss Greece's economic programme.