Moscow - President Vladimir Putin said 755 US diplomats must leave Russia and warned ties with Washington could be gridlocked for a long time, in a move on Sunday that followed tough new American sanctions.The Russian foreign ministry had earlier demanded Washington cut its diplomatic presence in Russia by September to 455 - the same number Moscow has in the US."More than a thousand people were working and are still working" at the US embassy and consulates, Putin said in an interview with Rossia-24 television. "755 people must stop their activities in Russia."Putin added that an upturn in Russia's relations with Washington could not be expected "any time soon"."We have waited long enough, hoping that the situation would perhaps change for the better," he said."But it seems that even if the situation is changing, it's not for any time soon."On Thursday, the US Senate overwhelmingly approved a bill to toughen sanctions on Russia for allegedly meddling in the 2016 US presidential election and for its annexation of Crimea in 2014.Iran and North Korea are also targeted in the sanctions bill.The law now goes to President Donald Trump who had made an improvement in ties with Russia a plank of his election campaign.Moscow on Friday ordered the US to slash its number of diplomats in Russia to 455 and froze two embassy compounds - a Moscow summer house and a storage facility in the city - from August 1.In December, the then US president Barack Obama ordered out 35 Russian diplomats and closed down two embassy summer houses that Washington said were being used by Moscow for espionage.