EU ambassadors are meeting to discuss on imposing new sanctions against Russia.
All 28 member states have agreed in principle to the new sanctions but the Finnish Prime Minister Alex Stubb, speaking at a press conference in Helsinki, said Finland had concerns about the timing of sanctions and about the effect of possible Russian counter-measures.
Mr Stubb said in particular that he wanted clarity about how new sanctions could be suspended if the ceasefire in eastern Ukraine continued.
Major state-owned oil firms including Rosneft are on the new EU sanctions list, but gas is not affected, diplomats say. US sanctions already target Rosneft.
Russia has warned that it could block international flights through its airspace if the EU goes ahead with new measures.
Diplomats say the new package will target Russian oil companies Rosneft and Transneft and the petroleum unit of state gas monopoly Gazprom.
Their access to financial markets will be restricted – a serious matter for Rosneft, which last month asked the Russian government for a $42bn (£25.2bn) loan.
However, European Commission’s Pia Ahrenkilde-Hansen said “The sanctions package can be extended or stopped, depending on developments in the field.”