They said ambassadors from the EU's 28 member states were to meet next week on Wednesday to roll-over punitive measures first adopted after the July 2014 downing of a Malaysia Airlines jet, blamed on pro-Russian rebels in eastern Ukraine.
"It is looking like it will be a rollover for another six months," one diplomatic source told AFP.
Amid differences over what line to take as Brussels and Washington seek Russia's help to resolve the Syrian conflict, the sources said the simplest option was to extend the measures.
"There was a discussion. Poland wanted to put more sanctions on Russia, others less, so in the end there was a tendency to leave them as they are and extend them for six months," another diplomatic source said.
"We want to do this without too much fuss and we do not want to discuss the issue at the summit in December," the source said.
Many eastern European member states are notably more critical of Moscow, fearing Russian intervention in Ukraine shows it wants to reassert its Soviet era influence in the region.
In March, EU leaders agreed to link the economic sanctions to Russia's full implementation of a ceasefire brokered by France and Germany in Minsk.
The first diplomatic source said the decision "will allow us to step back a bit, give us some time" to see what happens next with the Minsk peace accords.
A fresh Franco-German initiative helped bolster the Minsk accord in September, producing a marked decline in ceasefire violations and hopes the agreement might stick after the rebels agreed to postpone elections in areas they control until next year.
The EU has also imposed separate travel ban and asset freeze sanctions on Russian and Ukrainian individuals held responsible for backing the rebels, which run to March, and for those involved in Moscow's annexation of Crimea, which run to June.
