President Barack Obama and Chancellor Angela Merkel say sanction on Russia, imposed due to the Ukraine crisis, must remain until a deal to end the fighting is implemented.
The two leaders met during the G7 economic summit, currently ongoing in southern Germany.
The White House issued a statement after Mr Obama's talks with Ms Merkel, saying: "The duration of sanctions should be clearly linked to Russia's full implementation of the Minsk agreements and respect for Ukraine's sovereignty."
Russian President Vladimir Putin said on Saturday that Russia was not a threat and had "other things to worry about".
He told the Italian newspaper Corriere della Sera: "Only an insane person and only in a dream can imagine that Russia would suddenly attack Nato.
The European Union's President of the Council of Ministers, Donald Tusk, also signalled a toughening of sanctions in a statement at the G7, while EU sanctions are due to expire at the end of July.
"If anyone wants to start a debate about changing the sanctions regime, the discussion could only be about strengthening it."
Prime Minister David Cameron said he was hopeful that there would be a united front to ensure that sanctions were "rolled over" despite admitting that "sanctions are having an impact on all of us".
