By Andrey Ostroukh

MOSCOW--Russia will decide whether it should use fiscal stimulus to support its flagging economy after assessing the impact of including Crimea, the prime minister said Friday.

Moscow is seeking ways to kick-start the country's economy, which could contract if the Ukraine crisis and sanctions against Russia keep capital outflows at levels seen so far this year.

"We need to understand whether economic conditions have changed to such an extent that we would have to alter our fiscal rule. For example, does the Crimea entry change economic conditions or not? Do these 2.5 million people change macroeconomic parameters?," Dmitry Medvedev said.

The economy ministry repeatedly has said that given the risks of economic contraction, Russia should ease its so-called fiscal rule, through which the government puts much of the revenue generated by high oil prices into special rainy-day funds.

The finance ministry has long opposed alerting the rule, saying that though Crimea will demand extra funds from Russia, the region's inclusion shouldn't increase the country's budget deficit.

Mr. Medvedev said the fiscal rule should be "adequate" to meet conditions, but if these change dramatically, the government's fiscal toolkit should be revised.

Russia, which has a population of more than 140 million people, annexed Crimea after a referendum there on March 16.

Write to Andrey Ostroukh at andrey.ostroukh@wsj.com