* Sanctions were annulled after decision by EU court
* New regulation to be published on Saturday (Updates with outcome of meeting)
By Barbara Lewis and Robin Emmott
BRUSSELS, Feb 12 (Reuters) - European Union governments agreed on Thursday to put the National Iranian Tanker Company (NITC), Iran's biggest tanker firm, back on a list of sanctioned firms.
The EU's second-highest court ruled last July there were no grounds to blacklist the NITC after it contested the designation, but the EU moved to re-impose sanctions on tighter legal grounds.
The decision to put the tanker firm back on the sanctions list was taken by an EU working group on Thursday. The regulation will be published in the EU's Official Journal on Saturday.
NITC - a major transporter of Iran's oil - contested the EU's original blacklisting last year, arguing that the firm is privately owned by Iranian pension funds. It has denied any links with the Iranian government or with the Revolutionary Guards.
A copy of an EU letter to the NITC's lawyers, seen by Reuters, said the EU disagreed with their arguments that the NITC did not provide financial support to the government of Iran and therefore should not be sanctioned.
"You acknowledge that NITC's shareholders are entities providing pensions and other social benefits, and social security is a responsibility of the Iranian government," the letter said.
The EU had therefore decided to include the NITC again on "the list of persons and entities subject to restrictive measures", or sanctions, it said.
The sanctions - originally imposed in 2012 over Tehran's disputed nuclear programme - prohibited any trade between the EU, its companies and citizens, and the NITC, including the provision of services such as insurance or banking.
NITC officials could not be reached for comment.
The EU has also decided to re-impose sanctions on Iranian businessman Gholam Golparvar, who, the EU says, has links to Islamic Republic of Iran Shipping Lines, Iran's top cargo shipping group, EU documents showed.
The General Court had annulled sanctions against him and some other Iranian businessmen in December 2013, saying the listings were legally faulty.
The decisions fall at a sensitive time in negotiations to resolve a 12-year standoff between Tehran and the West over its nuclear programme. Diplomats stress the EU is not imposing fresh sanctions, only changing the criteria to make them legally watertight.
Under last year's accord between Iran and the United States, France, Germany, Russia, China and Britain, the Islamic Republic halted its most sensitive nuclear activity and took other steps in exchange for some easing of economic sanctions. (Additional reporting by Adrian Croft in Brussels and Jonathan Saul in London; editing by Ralph Boulton)