WASHINGTON, Dec. 21 - Millions of dollars' worth of U.S.-supplied drones that Kiev had hoped would help in its war against Russian-backed separatists have proven ineffective against jamming and hacking, Reuters reported Wednesday, citing Ukrainian officials.

The 72 Raven RQ-11B Analog mini-drones were so disappointing following their arrival this summer that Natan Chazin, an advisor to Ukraine's military with deep knowledge of the country's drone program, said if it were up to him, he would return them.

"From the beginning, it was the wrong decision to use these drones in our (conflict)," Chazin, an advisor to the chief of the general staff of Ukraine's armed forces, told Reuters.

The hand-launched Ravens were one of the recent highlights of U.S. security assistance to Ukraine, aiming to give Kiev's military portable, light-weight, unarmed surveillance drones that were small enough to be used widely in the field. They are made by AeroVironment.

But they appear to have fallen short in a battle against the separatists, who benefit from far more sophisticated military technology than insurgencies the West has contended with in Afghanistan, Iraq or Syria.

The Air Force command of Ukraine's armed forces acknowledged to Reuters that the Ravens supplied by the United States had a fundamental drawback: Russia and the separatist forces it supports can intercept and jam their video feeds and data.

"The complex is analog, therefore command channels and data are not protected from interception and suppression by modern means of electronic warfare," it said.

U.S. officials, speaking on condition of anonymity, acknowledged that Russia's electronic warfare capabilities were far more sophisticated than thought when the conflict began and that both the U.S. and Ukrainian militaries were adapting.

The U.S. Army uses Ravens but has upgraded to digital versions.

Chazin said the drones were largely in storage and called them a vulnerability, allowing the enemy to see Ukrainian military positions and, when it wanted, easily take them down. They had short battery life and were unable to reliably fulfill the key mission of gaining intelligence on artillery positions, he said.

"(Analog) basically puts you back in the stone age of the UAVs," said James Lewis, director of the strategic technologies program at the Center for Strategic and International Studies, using an acronym for Unmanned Aerial Vehicles, or drones.

One of the U.S. officials cautioned about limitations on America's ability to export drones that can evade Russia's electronic warfare capabilities.

That could leave Ukraine's military to continue building drones from commercially available technology. It now assembles them from components supplied by firms in countries such as Australia, China and the Czech Republic for only $20,000 to $25,000 apiece, Chazin said, and they are more advanced than the more pricey Ravens, which are often funded from private donations. (rt/ez)