Turkey warned France on Friday their political and economic relations would suffer grave consequences if the French parliament passed a draft law making it illegal to deny the 1915 mass killing of Armenians in the Ottoman Empire was genocide.

French President Nicolas Sarkozy, a vocal critic of Turkey's long-standing, but slow-moving bid to join the European Union, told Turkey in October that unless it recognised the killings as genocide, France would consider making denial a crime.

The draft law, put forward by a deputy from Sarkozy's party, is due to go before parliament next Thursday and proposes a one-year prison sentence and 45,000 euro (37,722.47 pounds) fine for denying the killings constitute genocide.

This proposed law targets and is hostile to the Republic of Turkey, the Turkish nation and the Turkish community living in France, Turkish Prime Minister Tayyip Erdogan wrote in a letter to Sarkozy.

I want to state clearly that such steps will have grave consequences for future relations between Turkey and France in political, economic, cultural and all areas and the responsibility will rest with those behind this initiative, said the letter quoted by the state-run Anatolian news agency.

France is Turkey's fifth biggest export market and sixth biggest country from which it imports goods and services.

Armenia, backed by many historians and parliaments, says some 1.5 million Christian Armenians were killed in what is now eastern Turkey during World War One in a deliberate policy of genocide ordered by the Ottoman government.

Ankara denies the killings constitute genocide and says many Muslim Turks and Kurds were also put to death as Russian troops invaded eastern Anatolia, often aided by Armenian militias.

ERDOGAN CALLS FOR COMMON SENSE

The French Foreign Ministry stressed the draft law was not a government initiative.

Turkey is a key ally and partner for France. We attach the highest value to our relations with Ankara, particularly on international and regional affairs, said ministry spokesman Bernard Valero.

Erdogan said common sense should prevail over political calculations, a hint the draft law was aimed at securing the support of 500,000 French voters of Armenian descent in elections due in five months time.

Turkish-French relations should not be held captive by the demands of third parties, Erdogan said. This is a sensitive, serious subject.

Turkey and Armenia signed a peace accord in 2009, agreeing to set up a commission of international experts to examine the events of 1915, restore diplomatic ties and open their border to trade, but neither side has ratified the deal.

Turkey shut its border with Armenia in 1993 over Yerevan's backing for Armenian separatists fighting Turkic-speaking Azerbaijan for control of Nagorno-Karabakh. Erdogan said at the time the deal with Armenia would only go ahead if the frozen Nagorno-Karabakh conflict was resolved.

Turkey has increasingly flexed its rising economic and political muscle on the world stage and in the Middle East as its economy continues to show strong growth while western Europe suffers a financial crisis.

(Additional reporting by Leigh Thomas in Paris; Editing by Philippa Fletcher and Matthew Jones)