The EU says new sanctions against Russia should be adopted shortly and take effect on Tuesday, despite a Kremlin warning of retaliation.
But an EU spokeswoman said the sanctions would be “reversible”, depending on the situation in Ukraine.
Pro-Russian rebels and government troops are observing a fragile truce.
Russia has warned that it could block international flights through its airspace if the EU goes ahead with new measures over the Ukraine conflict.
The pro-Russian separatists have recently made big gains in eastern Ukraine. But a ceasefire agreed on Friday appears to be holding despite some sporadic shooting.
Fighting in the east has killed some 2,600 people since April.
Russia has repeatedly denied accusations by Ukraine and the West that it has been sending troops into Donetsk and Luhansk regions to help the rebels, who want to establish an independent state.
A European Commission spokeswoman said the new sanctions package targeting Russian firms and officials “is due to be formally adopted by member states through a written procedure later today, so the procedure is ongoing”.
“It will then be published in the official journal of the EU, which should happen in the course of tomorrow at the latest as plans currently stand,” she said.