LONDON: Libya's National Oil Corporation (NOC) on Wednesday lifted force majeure at the Es Sider oil terminal, but said guards had blocked a tanker from loading, preventing a resumption of exports.

"We have recently received a formal security assessment concerning Es Sider Terminal, which confirms that vessel on standby can load upon arrival," a document circulated to oil traders and seen by Reuters said.

But in a statement later on Wednesday, NOC said the Petroleum Facilities Guards prevented the tanker entering the port.

The Delta Ocean Suezmax tanker arrived at the port on July 5, Refinitiv Eikon data showed. It was chartered by trader Unipec, a shipping and a trading source said.

The other eastern ports of Ras Lanuf, Brega, Zueitina and Hariga, have been under force majeure, which allows contractual obligations to be ignored, since January because of a blockade imposed by forces in eastern Libya.

Libya's Zawia oil terminal, home to a refinery, is not exporting crude following the shutdown of the Sharara oilfield.

The blockades have resulted in $6.5 billion in lost revenue for OPEC member Libya, whose production of around 100,000 barrels per day (bpd) is a small fraction of its 1.6 million bpd pre-civil war output level.

Already shutdowns have reduced capacity to 1.2 million bpd and the current blockade risks cutting it further to 650,000 bpd in 2022, NOC Chairman Mustafa Sanalla said on Tuesday.

A return of Libyan barrels to the oil market, as a resurgence in coronavirus infections weakens the demand outlook, could complicate matters for the Organization of the Petroleum Exporting Countries and its allies as they curb output to bolster the market.

Brent crude was, however, little changed around $43 per barrel on Wednesday.

"Based on experiences earlier this year ... I guess market participants believe in recovering Libyan oil production only when they see it," UBS analyst Giovanni Staunovo said.

Last month, a restart of Sharara, the country's biggest oilfield, was short-lived.