Judge Adrian Fulford said he first had to consider the prosecution's request before he could consider freeing Lubanga.
The case was suspended last week over concerns that Lubanga could be denied a fair trial due to withheld evidence.
The trial had been due to start on Monday, but judges postponed it following complaints from the defence that prosecutors had not handed over about 200 documents.
Lubanga's defence team told the court that the halt to proceedings should automatically trigger his release.
However, Ekkehard Withopf, for the prosecution, said: "There is no legal basis for the request."
Meanwhile, Carine Bapita Buyangandu, a lawyer representing the victims, warned the release of Lubanga could reignite conflict in Congo's Ituri region, where Lubanga stands accused of conscripting children under the age of 15 to fight soldiers.
"There will be a fire ball in Ituri and we will all be held accountable throughout history for this. We have waited 20 months," she said.