Eastern rebel leaders vying for more autonomy over a region known as Cyrenaica blocked the export terminals of Es Sider, Ras Lanuf and Zueitina in July.
The Libyan government in early April reached a deal with eastern rebel leaders to re-open the ports. Merghani said, however, the long closure meant operations couldn't return to normal.
"There is some damage (at Zueitina port) due to the long closure," he said Sunday.
Libya before civil war erupted in 2011 was exporting more than 1.4 million bpd. The Organization of Petroleum Exporting Countries said member state Libya produced less than 300,000 bpd in March, the last full month for which data are available.
The justice minister said the central government and rebel negotiators were still at odds over who would sit on a committee that would investigate claims of corruption within the oil sector.
A March report from the European Commission said the blockade on eastern oil export terminals has "severely" affected Libya's fiscal situation.
[Maritime Activity Reports]