Ukraine's president, Petro Poroshenko, has said he expects Ukraine to join the European Union eventually, and said Europe would be safer, richer and younger with his war-torn country as a member.

Speaking at a summit in Kiev attended by senior EU leaders, Poroshenko said it would be "impolite" for Brussels to refuse Ukraine what he called a "membership perspective".

"A friend in need is a friend indeed," he said. He thanked EU states for imposing the latest round of sanctions against Russia, which were published on Friday, despite a tentative ceasefire in the east of Ukraine agreed last week.

The new sanctions impose tough financial penalties on Russia's biggest oil company, Rosneft, and on its banks and arms companies. The EU has made it harder for the firms to raise money from capital markets. It has also banned 24 Russian officials and frozen their assets. They include separatist leaders in Ukraine, four deputy parliamentary speakers, and Sergei Chemezov, an ex-KGB spy who served with Vladimir Putin in east Germany. The EU says he is one of Putin's close associates.

The moves are in response to what the EU claims is a campaign by Russia to destabilise Ukraine. Speaking on Friday, Poroshenko said that Ukraine was "one of the biggest parts" of Europe because of its size and people. "My personal idea is Europe simply can't be the European Union without Ukraine," he suggested.

He said bringing Ukraine inside the EU would make the bloc more stable and "culturally diversified". It would also "collapse" the idea that Ukraine had to be part of Russia's zone of influence.

There is little immediate prospect of Ukraine joining the EU. But the issue of European integration has been at the centre of the turmoil that has gripped the country since late last year, when Ukraine's then president, Viktor Yanukovych, tore up an association agreement with the EU and accepted a bailout from Russia.

Yanukovych's move triggered months of streets protests in the capital, Kiev, and led to him fleeing the country in February. Ukraine's new pro-western government then endorsed the agreement, signed by Poroshenko days after he became president in June. The EU and Ukrainian parliaments will simultaneously ratify the agreement next week.

Poroshenko said he had received unprecedented levels of support from EU leaders and the US, most recently at last week's Nato summit in Wales, in the wake of Russia's annexation of Crimea and its covert invasion of parts of eastern Ukraine.

"I feel a full member of the European family," he said. The president declined to criticise Putin directly. Instead he said "ambition and emotion" had driven the Kremlin's support for pro-Russia rebels.

He said the ceasefire agreed in Minsk last Friday was fragile but working. Poroshenko sketched out his plan to bring peace to the rebel-held Donestk and Luhansk regions. It involved devolving power to local municipalities without compromising his country's territorial integrity, he said.

The latest EU sanctions do not target Russia's gas industry – unsurprising, given Europe's reliance on Siberian gas. But they do deal a major blow to its oil businesses. EU companies are forbidden from signing new contracts involving drilling in Russia's Arctic, as well as deep sea and shale projects. BP holds a 19.75% stake in Rosneft, and said on Friday that it was still assessing the implications of the sanctions.

"We will have to look at the sanctions very carefully and will comply with them," said a BP spokesman in London.

In May, BP signed a separate shale gas cooperation agreement with Rosneft although drilling has not yet started. BP-branded petrol stations can still be seen around Moscow although they are now formally owned by Rosneft.

The sanctions also affect the Russian pipeline operator Transneft, a subsidiary of Russia's energy company Gazprom.

The US also unveiled further sanctions on Friday. It named a string of major Russian companies including Gazprom, the oil companies Lukoil and Rosneft, and Sberbank, Russia's largest bank.

Poroshenko made his remarks at the Yalta European strategy meeting, an annual summit held for the past decade in Crimea at the palace where Churchill, Roosevelt and Stalin agreed Europe's postwar settlement. This year it is being held in Kiev for the first time, with Tony Blair and Sir Richard Branson among the speakers.

Opening the event, Poroshenko said he expected Crimea to return to Ukraine, though he ruled out using military means to get it back.

Estonia's president, Toomas Hendrik Ilves, a well-known critic of Kremlin power, described 2014 as an annus horribilis for Europe and said Russia's cynical "dismemberment" and "invasion" of Ukraine had plunged the continent into its gravest crisis since the second world war.

"We have seen the fundamental tenets of security in Europe thrown out of the window," Ilves said. He compared Moscow's opportunistic land-grab in Crimea – justified by the need to "protect" ethnic Russians – to Hitler's annexation of Sudetenland.

Ilves also referred to Leviathan, Thomas Hobbes's 17th-century work of political philosophy. "What Russia has done is bring us back to 1648 and Hobbes's war of all against all," he said.

Martin Schulz, the European parliament president, said Ukraine's problems were Europe's problems. He said the EU was embroiled in an ideological battle between two worlds – one based on democracy, human rights and the rule of law, and the other on "fear, intimidation and oppression".

"Many of us are at a loss to understand the strategy of Russia and its motivation," he said. On sanctions, he added: "They are a clear signal. We Europeans are united on this. We're serious about this. We are so serious we are willing to accept the negative consequences of sanctions for our own economies."