* NATO says will deny access to Libya on case-by-case basis
* Tanker anchored off Tunisia, near Libyan border
* Diversion seen as tactic to win war - analyst
(Adds analyst, trade and NATO comment, background, details)
By David Brunnstrom and Jessica Donati
BRUSSELS/LONDON, May 20 (Reuters) - NATO said it had intercepted an oil tanker that the alliance had reason to believe was set to deliver fuel to military forces headed by Libyan leader Muammar Gaddafi.
Gaddafi’s government is seeking to raise fuel imports for military purposes and to keep civilian vehicles running in areas he controls.
International sanctions do not include a fuel embargo.
“NATO naval forces can deny access to vessels entering or leaving Libyan ports if there is reliable information to suggest that the vessel or its cargo will be used to support attacks or threats on civilians, either directly or indirectly,” NATO spokeswoman Carmen Romero said on Friday.
On Thursday the Malta-flagged Jupiter, with a capacity to carry between 10,000-15,000 tonnes of gasoline, was the first fuel tanker bound for a west-Libyan port known to have been forcibly diverted.
The move comes ahead of a possible European Union initiative to tighten sanctions on the government of the Libyan leader by blacklisting ports to prevent exports of oil and imports of fuel. [ID:nLDE74I1U9]
United Nations resolution 1973 authorised the enforcement of a no-fly zone over Libya and “all necessary measures” to protect civilians.
“If they can choke off supplies, then it will make a difference. They (NATO) are ratcheting up the war effort to try to finish it off quickly,” said Charles Gurdon, managing director of London-based political risk consultancy Menas Associates.
The NATO spokeswoman denied that the diversion represented a change in policy, adding that decisions on whether to divert vessels would be taken on a case-by-case basis.
The tanker is now in the Tunisian port of Zarzis, according to three shipping sources, who added that the vessel had not yet unloaded its cargo because of fighting near the Libyan border.
The Jupiter was carrying gasoline bought from the Saras (SRS.MI) refinery in Sardinia by an unknown buyer and was bound for Malta, where it was instructed to head for a port in Libya, according to a shipping source.
It was not immediately clear who chartered it.
NATO said it hailed and boarded a Libyan-flagged vessel owned by state-owned shipping company General National Maritime Transport Company in late April but let it go on the grounds it was empty.
Trading sources said the latest NATO move was likely to deter other firms from oil trade with west Libya.
“I thought that NATO was going to allow commercial shipping traffic including oil. But if they are intercepting vessels, then who knows what they will do next,” said a source in an oil trading firm active in the Mediterranean.
“For us it’s just not worth it.”
A crude oil tanker owned by Libyan shipping company GNMTC was due to arrive empty on Thursday at the Gaddafi-controlled port of Ras Lanuf but has since switched its destination to Malta and is sailing nearby, according to AIS live tracking data on Reuters.
Reuters reported earlier this week that a fuel tanker, the Libyan-flagged Cartagena, was on its way to west Libya after visiting Turkish and Georgian ports. [ID:nLDE74H1S0]
It was last seen on Friday near Malta, AIS data showed. Shipping sources said it was also expected to arrive in Tunisia early on Saturday.
Writing by Emma Farge; editing by Jane Baird