Russia on Tuesday condemned the United States' decision to ease restrictions on arming anti-government rebels in Syria as a "direct threat" to its forces in the region.

Moscow has been launching airstrikes in Syria on behalf of President Bashar Assad and government forces in a years-long conflict with rebels. Government rebels recently retook Aleppo from rebel forces.

Last week, President Obama signed the $600 billion-plus National Defense Authorization Act into law, which eases some restrictions on weapons supplies to rebels. The law does not sit well with Moscow.

"In the administration of B. Obama they must understand that any weapons handed over will quickly end up in the hands of jihadists with whom the sham 'moderate' opposition have long acted jointly," Russian Foreign Ministry spokeswoman Maria Zakharova said in a statement.

She added: "Such a decision is a direct threat to the Russian air force, to other Russian military personnel, and to our embassy in Syria, which has come under fire more than once. We therefore view the step as a hostile one."

Zakharova went on to accuse the Obama administration of "planting a landmine" for President-elect Trump in an attempt to push Washington's "anti-Russian line" into his incoming administration.

Throughout his presidential election, Trump expressed interest in improving relations with Russian President Vladimir Putin and Moscow as a whole.

"We hope that those who succeed them will be wiser," Zakharova said of Trump's administration.

Zakharova also said it was unclear how Russia threatens NATO members.

"It is unclear how we threaten the sovereignty and territorial integrity of NATO countries," she said. "After all, the Americans and their allies demonstrate increased military activity, push the boundaries of the alliance and bring their military capability closer to our borders. Naturally, we have to take into account such developments in the implementation of our own programs of development of the armed forces."