President Barack Obama and Chancellor Angela Merkel held talks as the G7 summit of economic powers began in southern Germany, BBC reports.
Moscow is the target of European Union and US sanctions over its role in support of Ukrainian rebels.
Russia has been excluded from what was previously known as the G8, since the annexation of Crimea last year.
The West accuses Russia of sending military forces into eastern Ukraine to help the rebels – a charge echoed by analysts. Moscow denies this, saying any Russian soldiers there are volunteers.
As he arrived in the Bavarian Alps, President Obama said G7 leaders would discuss “standing up to Russian aggression” in Ukraine.
The White House issued a statement after President Obama’s talks with Chancellor 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.”
Germany, Britain and the US want an agreement to offer support to any EU member state tempted to withdraw backing for the sanctions on Moscow, which are hurting the Russian economy.
The European Union’s President of the Council of Ministers, Donald Tusk, signalled a toughening of sanctions in a statement at the G7.
“If anyone wants to start a debate about changing the sanctions regime, the discussion could only be about strengthening it.”
UK 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”.
EU sanctions are due to expire at the end of July.
UK Foreign Secretary Philip Hammond echoed concerns about wider Russian military pressure. But, when asked if the US should redeploy intermediate-range nuclear missiles in Europe, Mr Hammond said the West had a “delicate act to perform”.
“We’ve got to send a clear signal to Russia that we will not allow them to transgress our red lines. At the same time we have to recognise that the Russians do have a sense of being surrounded and under attack, and we don’t want to make unnecessary provocations.”