Donald Trump has grudgingly approved a package of new sanctions on Russia that limits his own authority to reverse or relax them, signing the bill behind closed doors and voicing strong objections to the measures.

Trump took the unusual step of issuing two statements to accompany his signature, in which he said he had given his approval “for the sake of national unity” while calling the congressional bill “seriously flawed” and “clearly unconstitutional”.

In a sign that the president might seek to mitigate the impact of the bill in its implementation, he said would give “respectful consideration to the preferences” expressed by Congress in its provisions but would “implement them in a manner consistent with the President’s constitutional authority to conduct foreign relations”.

Trump had little choice but to sign the bill, which also includes expanded sanctions on Iran and North Korea. It was passed in the Senate by 98 votes to two and in the House of Representatives by 419 to three, so a presidential veto would have been easily overturned by a Congress that is wary of Trump’s ties to Moscow.

Russia’s prime minister Dmitry Medvedev said the sanctions were tantamount to a “full-scale trade war”.

“The hope that our relations with the new American administration would improve is finished,” he wrote in a Facebook post.

“Trump’s administration has demonstrated total impotence by surrendering its executive authority to Congress in the most humiliating way,” wrote Medvedev, who presided during a brief period of improved relations early in Obama’s presidency.

“The US establishment fully outwitted Trump; the president is not happy about the new sanctions, yet he could not but sign the bill.”

But the new Russian ambassador to the United Nations, Vasily Nebeznya indicated that Moscow would continue to seek common ground with the Trump administration.

“We will not relent on finding ways and means to cooperate with our partners, including the United States,” Nebeznya said.

The sanctions bill is one of the most consequential pieces of legislation Congress has put on the president’s desk in the six months of the administration, but Trump signed it into law without a ceremony, which is customary for major new laws, and without even letting cameras into the Oval Office to record the event.

His signature was accompanied by two statements expressing reservations about the bill. They are similar in content but the first is more legalistic and the second more personal in tone, boasting that he had “built a truly great company worth many billions of dollars” and “I can make far better deals with foreign countries than Congress”.

Trump’s objections focused on the section of the bill that limits his ability to relax sanctions on Russia without approval from Congress. He said “it encroaches on the executive branch’s authority to negotiate”.

“By limiting the Executive’s flexibility, this bill makes it harder for the United States to strike good deals for the American people, and will drive China, Russia, and North Korea much closer together,” his statement said. “The framers of our constitution put foreign affairs in the hands of the president. This bill will prove the wisdom of that choice.”

The most controversial section of the bill prohibits the Trump from lifting sanctions on Russia or even easing their impact without first reporting to Congress on what the US will get in return from Moscow.

Donald Trump with Vladimir Putin at the G20 summit in Hamburg in July. Photograph: Evan Vucci/AP

Adam Smith, the director of multilateral affairs in Barack Obama’s national security council, said that the congressional measure was “was somewhat unprecedented in tying the president’s hands”.

However, he said that the Trump administration would still have considerable wiggle room in how it chooses it interprets and implements the sanctions measures.

“There are delay tactics. The executive does not have to disobey a law in order not to execute it,” said Smith, now a partner at the Gibson Dunn international law firm. “The president can direct the blow in a way more in line with his foreign policy desires.”

Moscow has already retaliated for the new sanctions, ordering the US to cut its diplomatic staff in Russia by 60%, obliging the embassy to make many of the Russian staff redundant. On Wednesday, the Russian authorities took over a dacha compound that had been leased by the US embassy on the outskirts of Moscow.

In one of his statements, Trump sought to soften the punitive intent of the sanctions, claiming the bill “represents the will of the American people to see Russia take steps to improve relations with the United States”.

“We hope there will be cooperation between our two countries on major global issues so that these sanctions will no longer be necessary,” he said. In his response, Nebeznya said if the bill was meant to encourage better relations, it was “a strange sort of encouragement.”

“Those who invented this bill, if they were thinking they might change our policy, they were wrong,” the Russian diplomat said. “They should have known better, that we do not bend, we do not break.”

Jean-Claude Juncker, president of the European commission, claimed to be satisfied that the US had limited the reach of sanctions against Russia in response to the EU threat’s to hit back if European interests were impacted.

“I stated at the G7 summit in Taormina, Italy, and at the G20 summit in Hamburg, Germany, that if the Americans proceeded [with the adoption of new sanctions], we would be ready to react adequately in a matter of days,” Juncker said in a statement.

“As a result, a significant proportion of the intended sanctions against Russia have been dropped. Moreover, US Congress has now also committed that sanctions will only be applied after the country’s allies are consulted. And I do believe we are still allies of the US”.



Brussels, however, warned that if they concluded sanctions did specifically disadvantage EU companies trading with Russia , the EU was still prepared to take appropriate steps in response within days. “We are prepared,” Juncker told the German broadcaster ARD on Wednesday. “We must defend our economic interests vis-à-vis the United States. And we will do that.”