The European Union and Russia have started talks on a new cooperation deal on political and economic ties the EU hopes will redefine the way it imports much of its oil and gas from its key supplier.

The EU wants Moscow to open its vast energy sector to European investors. Moscow has pushed for more opportunity for its companies to invest in oil and gas distribution networks in Europe.

The existing 10-year agreement, signed in 1997, remains in effect until a new one is made. But it has lost much of its meaning, thanks to Russia’s new oil and gas wealth and more assertive foreign policy stance.

At their first session Friday, negotiators will focus on defining the scope of the talks, the agenda and a calendar for the talks, which experts say could last more than a year.