The Biancocelesti revealed that the Bosnian will succeed Edy Reja and added that an official announcement will be made once discussions with the club president are completed
The 48-year-old will take charge of the Italian club less than a month after taking on a temporary coaching role at Swiss side Sion, who agreed to let the Bosnian leave without raising any objections.
He will replace Edy Reja, who left Lazio at the end of the season, with the official announcement from the Biancocelesti expected shortly.
"Petkovic visited the club's headquarters on Friday," De Martino told Lazio Style Radio.
"He spoke with sporting director Igli Tare and also with myself, but it was a quick chat since he spoke to Tare for a long time.
"We are now waiting for Lazio to make the announcement. We will see if it happens today or tomorrow. These have been long days.
"Let president Claudio Lotito have the time to discuss everything that needs to be discussed."
Petkovic, who took charge of Swiss side Young Boys between 2008 and 2011, stepped down as Samsunspor coach in January 2012 following a series of disappointing results prior to his move to Sion.