The EU has agreed new sanctions to be levelled against Russia.
But diplomats have delayed enforcing them so they can assess the situation on the ground in Ukraine.
European Council President Herman Van Rompuy said any decision would depend on whether the ceasefire there holds.
EU ambassadors meet again to discuss the issue on Wednesday.
Jacek Saryusz-Wolski, a Polish centre-right MEP, said: “Either this agreement on ceasefire is respected or there will be further escalation on the EU side in terms of sanctions.”
If implemented, the measures would target Russian state-owned oil firms and defence contractors.
Russia has warned of retaliation if any further sanctions are implemented.