Donald Trump is to sign a bill in the coming days that imposes fresh sanctions on Russia, the White House said.

The US Senate voted almost unanimously for the crackdown earlier this week for the legislation which forces Mr Trump to seek approval from Congress if he wishes to ease the sanctions.

As a result the US leader will have to take a hard line with Moscow after US intelligence agencies concluded that the Kremlin meddled in the 2016 presidential election to help Mr Trump pull off his shock victory.

It dashes his pledge for better ties with the Moscow as the agencies investigate whether his campaign colluded with Russian hackers to dig up dirt on his then White House rival Hillary Clinton.

Russia hit back after the sanctions were approved overwhelmingly in the Senate, accusing Washington of “extreme aggression in international affairs”.

Its Foreign Ministry also ordered the US to cut back its diplomatic staff in Moscow by 1 September and to shut down its embassy recreational retreat on the outskirts of the capital.

The White House last night issued a statement saying Mr Trump would sign the bill after reviewing the final version.

“President Donald J. Trump read early drafts of the bill and negotiated regarding critical elements of it,” the White House statement said. “He has now reviewed the final version and, based on its responsiveness to his negotiations, approves the bill and intends to sign it.”

Analysts said the US president was under pressure to sign the bill or face anger from Republicans. His new White House communications director Anthony Scaramucci told CNN that the U.S president may veto the legislation.

The fresh package of sanctions targets Russia's aggression in Ukraine and Syria, citing corruption, human rights abuses and weapons sales.

The bill also aims to hit Vladimir Putin and his inner circle by targeting alleged corrupt officials, and crucial sectors of Russia’s fragile economy, including its energy sector.

Russia's Foreign Ministry dismissed the new sanctions as "creating unfair competitive advantages for the US economy”.

"This kind of blackmail aimed at restricting the cooperation between Russia and other nations is a threat for many countries and global businesses," the statement said.

Russian policemen stand guard in front of the US Embassy in Moscow (AFP/Getty Images)

Russia's response to order the US to cut its number of diplomats in Moscow mirrors moves by outgoing President Barack Obama last December to expel 35 Russian diplomats and shut down two Russian estates in the US.

The Kremlin had previously said that it would not impose any sanctions on the US until Mr Trump signs the bill - which he is expected to do in the coming days.