Story highlights Imagery shows burn marks on the Russian side of the border, indicating artillery was fired

The EU steps up pressure against Russia for fomenting the Ukraine crisis

The Pentagon says the weaponry transfer could be "imminent"

Russia is preparing the transfer of more powerful weaponry into Ukraine, and it could happen at any time, a Pentagon spokesman said Friday, citing the latest U.S. intelligence.

The transfer could be "imminent," the spokesman, Col. Steve Warren, told reporters. It's believed the weaponry will be driven into Ukraine "potentially today," he said, but it is not clear if Russian troops will be involved.

State Department spokeswoman Marie Harf also warned of the possibility Thursday, telling reporters, "We have new evidence that the Russians intend to deliver heavier and more powerful multiple rocket launchers to the separatist forces in Ukraine and have evidence that Russia is firing artillery from within Russia to attack Ukrainian military positions."

The United States has imagery showing weaponry, with burn marks in the grass, on the Russian side of the border, indicating that artillery was fired, a U.S. official tells CNN. The images remain classified and were not shared with CNN.

The Russian military has more powerful rocket launcher systems than the ones that have been sent across the border in the past. Intelligence indicates just under a dozen systems may be part of this latest shipment, according to a U.S. official.

Everything Russia is doing, Warren said, is "unquestionably an escalation."

Earlier Friday, the European Union stepped up pressure against Russians and others it blames for fomenting the crisis in Ukraine, banning visas and freezing the assets of 15 more people and 18 more companies and organizations.

The EU's move, which aims to punish those supporting a months-long pro-Russian rebellion in eastern Ukraine, comes as international pressure was stepped up on the rebels in a related issue: the discovery and return of more victims' remains from last week's crash of Malaysia Airlines Flight 17 in rebel-held territory.

Details about who was sanctioned Friday weren't immediately available. But the EU and the United States previously have targeted Russians and Ukrainians they say have assisted the rebellion and Russia's annexation in March of the Ukrainian Black Sea peninsula of Crimea -- such as Vladimir Shamanov, commander of Russian airborne troops.

The move brings the total number of EU sanctions in the Ukraine crisis to 87, and the number of entities to 20. The EU on Friday also widened its criteria for future sanctions, saying it would now look to punish not only those who are aiding the rebellion, but also those benefiting "from Russian decision makers responsible" for it.