"It would increase Russia's leverage over Europe's foreign policy and Europe's vulnerability to a supply disruption," Perry told an energy forum in the Lithuanian capital.
In his words, Nord Stream and TurkStream, the gas pipelines set to connect Russia with Germany and Turkey, "would enable Moscow to end gas transit through Ukraine by the close of the decade".
"Nord Stream 2 would deliver a stunning blow to Europe's energy diversity and security," Perry said.
The construction of the almost complete Nord Stream 2 gas pipeline is led by Russian gas giant Gazprom. The project is financed by German, Dutch, Austrian and French companies.
The pipeline's supporters say it will bring gas prices down, but Perry says Moscow will be able to use its power to bend other countries to its own will.
"It would transport a single source of supply from a single country providing that supply using a single route to deliver that supply in a way that exploits dependent nations, bending them to Moscow’s will," Perry said.
He also underlined that American LNG could bolster Europe's energy security. The US energy secretary also said in Vilnius that his country would seek to strengthen ties with Central and Eastern European countries in the area of energy.
He also announced plans to set up four working groups for that purpose and they would be responsible for energy efficiency and renewable resources, nuclear energy, supply security and the protection of critical infrastructure. The latter group will be led by Lithuania.
Perry also voiced plans to set up expert teams to help states identify flaws in their energy systems, including the risks of cyber attacks.