SOFIA, Feb 24 (Reuters) - Bulgarian truckers will stage another counter-blockade at all checkpoints on the country's border with Greece if Greek protesters do not end their own blockade by Monday, the Bulgarian transport minister said on Wednesday.

Greek farmers have been intermittently blocking roads into Bulgaria and motorways across Greece for about five weeks, protesting pension reforms that will triple their social security contributions over the next four years.

"If the Greek side does not find, in whatever form, a way of resolving the crisis by Monday, Bulgarian road carriers will launch a counter-blockade along the entire Bulgarian-Greek border," Transport Minister Ivaylo Moskovski said.

The counter-blockade will focus only on vans, cars, and large vehicles transporting agricultural goods.

"We decided to block not only agricultural production entering and leaving Bulgaria but also such (goods) for which Bulgaria is a transit country," Mirolyub Stolarski, the head of the Bulgarian association of road transport union, said, adding that they also plan to block the border with Macedonia for Greece's agricultural production.

Last week, the Bulgarian road carriers have already staged a counter-blockade after the Greek protesters failed to keep a promise to lift their blockade for a few hours a day.

The blockade was lifted on Sunday but then resumed on Tuesday after talks between protesting farmers and Greek Prime Minister Alexis Tsipras failed.

Bulgarian authorities saying the carriers' losses would exceed 10 million euros ($10.96 million). The blockage created a 10-km (6-mile) queue of trucks on the Bulgarian side.

Bulgaria estimates serious losses for its tourism industry as well.

According to Nastimir Ananiev, chairman of the parliament's transport committee, about 40,000 Bulgarians have cancelled their holidays in Greece and around 30,000 Greek citizens have cancelled trips to Bulgaria because of the blockades.

Bulgaria has called on the European Commission to impose sanctions against Greece, saying that the blockades violate European Union principles on the free movement of goods and people. ($1 = 0.9123 euros) (Reporting by Angel Krasimirov, editing by Louise Heavens)

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