US Vice President Mike Pence has blasted as “unacceptable” Germany’s dependence on Russian energy and its failure to meet its military spending commitments as a key member of the NATO military alliance.

Pence told NATO�s 70th anniversary gathering in Washington, DC, on Wednesday that Berlin’s insistence on completing the Nord Stream 2 pipeline to buy Russian gas was not acceptable and undermined Europe’s security.

"Germany must do more. And we cannot ensure the defense of the West if our allies grow dependent on Russia," Pence told the two-day forum.

Washington has long taken issue with Germany’s plans to import Russian natural gas through the $11 billion pipeline project, which runs straight under the Baltic Sea.

The pipeline has also been criticized for depriving Ukraine, a staunch US ally, of lucrative gas transit fees.

Pence then repeated a warning by President Donald Trump that Berlin’s reliance on Russian energy would eventually make it a captive of Moscow.

"If Germany persists in building the Nord Stream 2 pipeline, as President Trump said, it could turn Germany�s economy into literally a captive of Russia," Pence said.

The vice president noted that the deal as well as Germany’s reluctance to meet the required military spending levels for all NATO members also undermined Europe’s deterrence power against what he called “Russian aggression.”

Trump has repeatedly slammed Germany and other members of the Western alliance for not meeting a goal set by NATO in 2014 for each member state to spend two percent of its GDP on defense.

"It is simply unacceptable for Europe�s largest economy to continue to ignore the threat of Russian aggression and neglect its own self-defense and our common defense," Pence said Wednesday.

Pence also pointed to a parliamentary report on Germany�s armed forces, which warned of "glaring deficiencies" in the country’s overall military readiness.

US warns German firms of sanctions over Russia ties

The US says German companies working with Russia’s energy sector could face sanctions under the CAATSA.

Germany, which remains opposed to nuclear power, has long sought for reliable sources of energy. However, the Nord Stream 2 pipeline has been met with strong criticism from the Baltic States – Latvia, Lithuania and Estonia – as well as Poland.

The US has even warned that German companies working with Russia on the project could face sanctions under the Countering America�s Adversaries Through Sanctions Act (CAATSA).

Germany and some other nations, have accused Washington of using the CAATSA to meddle in their foreign policy and energy affairs.

NATO chief calls for confronting Russia

Meanwhile, NATO Secretary General Jens Stoltenberg, who had been invited to deliver a speech to a joint session of Congress to mark the 70^th anniversary of the alliance, called for unity against an increasingly assertive Russia.

Stoltenberg claimed that NATO had been trying to avoid tensions with Russia but that Moscow’s behavior made confrontation inevitable.

He cited the Crimean Peninsula’s 2014 reintegration with Russia, Moscow’s alleged cyber aggression against the US and its support for Syria as examples of problematic Russian behavior.

“We do all of this, not to provoke a conflict, but to prevent conflict and to preserve peace. Not to fight but to deter. Not to attack but to defend,” he said during his 40-minute speech.

“There is no contradiction between the defense and dialogue. We do not want to isolate Russia. We strive for a better relationship with Russia."

The NATO chief did not address the alliance’s growing buildup on Russia’s borders, which has been a source of tension between the two sides since NATO unilaterally cut all ties with Moscow in 2014.

Stoltenberg also called on Russia to comply with the Intermediate-Range Nuclear Forces (INF), which has been halted by both Washington and Moscow, who accuse each other of breaching the deal.

“We do not want a new arms race. We do not want a new Cold War. But we must not be naive. An agreement that is only respected by one side will not keep us safe,” Stoltenberg said.