Prime Minister David Cameron has said he is hopeful that the G7 summit of world leaders will show "a united front against Russian-backed aggression" in Ukraine.
Mr Cameron acknowledged that the sanctions imposed on Moscow following the annexation of Crimea last year were also having "an impact" on European states, but made clear he wants them maintained when they come up for renewal at the end of July.
US President Barack Obama also said the summit in Germany would show the West's major industrialised states "standing up to Russian aggression in Ukraine".
Russia was ejected from the G8 last year because of its interference in Ukraine, where Western nations allege it has given military backing to separatist rebels in the east of the country – something President Vladimir Putin denies.
The two-day G7 summit hosted by German Chancellor Angela Merkel is the second gathering of the slimmed-down group of seven leaders since Russia's removal.
With Greece's Prime Minister Alexis Tsipras due to meet Putin on June 18 to discuss his country's debt crisis, there are concerns that Athens may break ranks and block the renewal of EU financial and economic sanctions at a Brussels summit at the end of the month.
Asked whether he would back financial incentives to keep on board countries such as Greece which have suffered as a result of the sanctions, Mr Cameron said: "Europe has been united on sanctions ... We need to make sure Europe remains united.
"It has an impact on all countries in terms of putting sanctions on another country. Britain hasn't let our pre-eminence in financial services get in the way of taking a robust response to Russian-backed aggression and I don't think other countries should either."
Arriving at the summit venue in the Bavarian Alps, the Prime Minister said: "I'm hoping for a good outcome where we can make sure that the sanctions are rolled over at the next European summit to show a united front against Russian-backed aggression".
And European Council president Donald Tusk told reporters: "If anyone wants to start a debate about changing the sanctions regime, the discussion could only be about strengthening them."
Mr Putin sought to play down Western concerns about Russia's military activities, amid reports of heightened tension in the east of Ukraine over the past few days.
He told the Italian newspaper Corriere della Sera that Moscow had "other things to worry about", adding: "Only an insane person and only in a dream can imagine that Russia would suddenly attack Nato."
The summit was taking place amid tight security in the spectacular mountain-top setting of Schloss Elmau, ringed by thousands of police. Demonstrators clashed with police in the nearby town of Garmisch-Partenkirchen, while a few hundred hiked up to the venue to protest outside its perimeter fence.
But there was a warm welcome for Mr Obama, who enjoyed a pre-summit lunch of German sausages and beer with Mrs Merkel, and revealed that he was hoping to buy some traditional Bavarian lederhosen - leather shorts - while he was there.
Campaign group One released giant balloons featuring the faces of the seven leaders - Mr Cameron, Mrs Merkel, Mr Obama, French President Francois Hollande and prime ministers Matteo Renzi of Italy, Shinzo Abe of Japan and Stephen Harper of Canada – in a plea for them not to "talk hot air" about global warming.
The German Chancellor has put climate change top of the agenda, with the aim of securing a united G7 position in favour of strong international agreement in Paris this November on measures to keep temperature rises below 2C.
Mr Cameron said the UK was "in the vanguard" of the drive for an ambitious European offer on climate change, and said he wanted to see the G7 "coming together and backing a strong deal in Paris".
The Prime Minister said he also wanted to see progress on issues ranging from Islamic State in Iraq and Syria, disease epidemics and the migrant crisis in the Mediterranean.
Following concern about the World Health Organisation's sluggish response to the Ebola virus in west Africa, he announced a new team of "disease detectives", putting UK experts on standby to fly to the location of new infection outbreaks within 48 hours.
And he hailed the success of Royal Navy warship HMS Bulwark in rescuing hundreds of migrants trying to cross from Libya into Europe by boat.
"We want to engage with these issues of international security, whether that's a more secure Iraq or Syria, whether it's conquering Ebola in west Africa, whether it's dealing with the crisis in the Mediterranean," said Mr Cameron.
"We do these things not just because we are a country with a conscience. We also do it because we know these things affect us back at home."
The Prime Minister called for concerted action by the G7 against corruption in organisations, businesses and governments around the world, in the wake of bribery allegations against Fifa.
"Whatever challenge you look at in the world, you find that corruption is often the cancer that stops us achieving what we want," said Mr Cameron.
"Why is it schoolgirls get abducted in Nigeria and we can't get them back? Corruption. Why is it that some people flock to join extremist groups in some parts of the world? Because of corrupt governments. Why are our efforts to turn countries from poverty to wealth often frustrated? Corruption."
He added: "Just as in the past I think too many people have taken the view when it came to Fifa that it was something we have to live with, we shouldn't just live with corruption, we should be fighting it with more vigour to help us tackle all these problems."
Mr Cameron also voiced concern over slow progress on the proposed US-EU Transatlantic Trade and Investment Partnership (TTIP), urging leaders to set a target of the end of 2015 to finalise political agreement.