MOSCOW, Aug. 3 (Xinhua) -- With a new sanctions bill enacted on Wednesday, the United States has declared a full-scale trade war against Russia, killing hope for easing the tension in bilateral relations, Russian Prime Minister Dmitry Medvedev has said.

"The hope of improving our relations with the new U.S. administration has come to an end," Medvedev said Wednesday on the social media Facebook, commenting on the signing into law of a new U.S. sanctions bill by U.S. President Donald Trump.

Calling it "significantly flawed", Trump on Wednesday signed into law the bill that also imposes sanctions against Tehran and Pyongyang. The bill was approved overwhelmingly in July by the U.S. Congress despite the White House urge for a "flexibility" in dealing with Russia, partly representing a bipartisan move to punish Moscow over its alleged meddling in the U.S. presidential election last year.

Trump's reluctant signature highlights more difficulties ahead in diplomatic efforts for both Washington and Moscow to resolve their conflict on such thorny issues as of the Middle East and Ukraine.

It also fully displays increasing troubles for Trump at home, such as crippled legislative agenda marked by failed efforts against his predecessor Barack Obama's signature health care system, in the aftermath of an alleged collusion with Russia of his campaign camp.

The Trump administration demonstrated "complete impotence, in the most humiliating manner, transferring executive powers to Congress," commented Medvedev.

As the new sanction regime makes it difficult to remove the measures against Moscow that may last decades, Medvedev foresaw little room for improving bilateral ties.

"The relationship between Russia and the United States will be extremely tense, regardless of the composition of the Congress or the personality of the president," he said.

The Russian prime minister slightly indicated a possible economic retaliation by saying that Russia will reduce reliance on western imports.

In a preemptive diplomatic move against the U.S. new sanctions, Russian President Vladimir Putin ordered Sunday a reduction of 755 staff in the U.S. diplomatic mission in Russia by Sept. 1.

Putin meanwhile voiced disappointment over Washington in an interview with a Russian TV station aired on Sunday.

"We waited for quite a long time that, perhaps, something will change for the better," said Putin. "But, judging by everything, if it (bilateral relationship) changes, it will not be soon."

Russian Foreign Ministry on Wednesday described in a statement the U.S. new sanctions as "short-sighted and even dangerous" while saying Moscow remains open to cooperation with Washington in various areas, including on the settlement of regional conflicts.

"However, fruitful cooperation is possible only if U.S. politicians overcome their own delusions and cease to perceive the world around them through a reality-distorting prism of 'American exclusiveness,'" the ministry said, adding that further retaliatory measures are possible.

On the enactment of U.S. new sanctions bill, Kremlin spokesperson Dmitry Peskov told Russian reporters that "De-facto this doesn't change anything," and that "retaliatory measures have already been taken".

U.S. Secretary of State Rex Tillerson said Tuesday he will meet with his Russian counterpart Sergei Lavrov over the weekend.