Putin, speaking on a visit to Finland, was commenting on a vote by the US House of Representatives which on Tuesday decided to impose new sanctions on Moscow and to force President Donald Trump to obtain lawmakers' permission before easing any sanctions on Russia.
The sanctions have yet to be approved by the Senate or Trump, and a top White House aide said on Thursday that Trump could veto the legislation in order to push for a tougher deal.
Putin, who has repeatedly denied US allegations that Russia interfered with last year's US presidential election, said Moscow would only decide on how to retaliate against Washington once it had seen the final text of the proposed law.
"As you know, we are exercising restraint and patience, but at some moment we'll have to retaliate. It's impossible to endlessly tolerate this boorishness towards our country," Putin told a joint news conference with his Finnish counterpart.
"When will our response follow? What will it be? That will depend on the final version of the draft law which is now being debated in the US Senate."
Putin also spoke about an ongoing diplomatic row between Moscow and Washington which erupted last December when then US President Barack Obama ordered the seizure of Russian diplomatic property in the United States and the expulsion of 35 Russian diplomats.
"This goes beyond all reasonable bounds," said Putin. "And now these sanctions - they are also absolutely unlawful from the point of view of international law."
Calling the proposed sanctions "extremely cynical," Putin said the demarche looked like an attempt by Washington to use its "geopolitical advantages ... to safeguard its economic interests at the expense of its allies".
He dismissed Congressional investigations into Russia's alleged meddling in last year's US presidential election, calling them a symptom of growing anti-Russian hysteria in the United States and a result of US domestic politics.
"It's very sad that US-Russian relations are being sacrificed to resolve internal policy issues in the US," said Putin. "It's a pity, because acting together we could be solving jointly the most acute problems that worry the peoples of Russia and the United States much more efficiently."
However, Putin said that Moscow had "many friends" in the United States and hoped that one day the situation would right itself.