US President Joe Biden's comment in which he called support for Ukraine and Israel an "investment" shows that Washington benefits from proxy wars rather than fights for ideas, a Russian foreign ministry spokeswoman said on Friday.

Biden said on Thursday that helping the two US allies was "a smart investment that's going to pay dividends for American security for generations", as he sought to rally support for new aid packages.

Russian foreign ministry spokeswoman Maria Zakharova said on the Telegram messaging app that Biden's comments betray a cynical approach.

"They used to call it 'fighting for freedom and democracy'," she said. "Now it turns out it is just calculations. It has always been that way, they just fooled the world using values for which Washington has never really stood."

"Nothing personal, just business," she said, using a comment made famous in the "Godfather" movie to sum up what she said was the true US stance on conflicts abroad.

"Wars have traditionally been 'smart investments' for the United States as they did not take place on the American soil and they do not care about costs borne by others," Zakharova said.