A combination of two photos shows U.S. President Donald Trump and Russian President Vladimir Putin as they arrive for the G20 leaders summit in Hamburg, Germany, July 7, 2017. (REUTERS/Carlos Barria/File Photo)

WASHINGTON, July 31 (Xinhua) -- In tit-for-tat move against Washington's looming sanctions against Moscow, President Vladimir Putin orders 755 U.S. diplomatic staff in Russia to be cut in what may be the sign of further escalation of revenge from both sides.

The move, which signaled Putin's growing impatience over improvement of Russia-U.S. relations, came after U.S. Congress passed new legislation that imposes additional sanctions on Russia. The White House has said U.S. President Donald Trump intended to sign the bill into law.

"This is a regrettable and uncalled-for act," the U.S. State Department said Monday in a statement. "We are assessing the impact of such a limitation and how we will respond to it."

"Combined with the shadow of Russian interference in the 2016 election, the political environment in the United States is hostile to Russia and Congress has led the way in skepticism of Russian policy and actions," Dan Mahaffee, Senior Vice President of Center for the Study of the Presidency and Congress, a Washington-based policy organization, told Xinhua in an interview.

Russia's decision to expel American diplomats marks the harshest such diplomatic move since the twilight years of the Cold War, but it is unclear how the order, which will take effect by Sept. 1, will be carried out.

Mark Galeotti, senior researcher at UMV, the Institute of International Relations Prague, held that Moscow's latest move will certainly inconvenience both the U.S. State Department and also any Russian wanting a U.S. visa or otherwise hoping to use the services of American's embassy and consulates there. It will be especially problematic for all those Russians employed by the U.S. government who will find themselves unemployed, said Galeotti.

The latest episode of Washington-Moscow tension further deteriorated the relationship between the two countries that has already been at a low point, and dealt a severe blow to Trump's efforts to mend ties with Russia.

"The Russian decision to reduce U.S. diplomatic staff appears linked directly to the new Congressional sanctions bill," Steven Pifer, Senior Fellow of the Brookings Institution, a Washington-based think tank, told Xinhua. "Neither action will help the U.S.-Russia relationship, which was already at a difficult level, but one should not overestimate the impact."

Pifer noted that U.S.-Russia relations are "at their lowest point since the end of the Cold War," adding that it will take "patient, hard diplomacy" to move the relationship to a better point.

Putin has ordered a dramatic reduction in the U.S. diplomatic mission to Russia, saying the U.S. diplomatic staff "will now equal the number of the Russian diplomatic personnel in the United States, 455 people on each side."

Last December, Trump's predecessor Barack Obama ordered 35 Russian diplomats to leave the U.S., saying the actions were being carried out in response to Moscow's alleged attempt to interfere in the election.

The row between the U.S. and Russia also signaled a major shift in tone from a summit between Trump and Putin earlier this month, which showed prospects of warmer ties.

"President Trump felt that he could improve U.S.-Russia relations with a strong personal rapport with President Putin, but given the deterioration of relations with Russia, the issues are far more than what can be resolved by a positive relationship between the leaders," Mahaffee said.