Ukraine’s newly unveiled parliamentary coalition has vowed to make NATO membership a priority, further cementing the country’s tilt towards the West.
It coincided with the first anniversary of the uprising which brought down pro-Russian President Yanukovych.
Prime Minister Arseniy Yatsenyuk keeps his job but President Poroshenko says the rest of the government must be completely renewed.
Ukraine’s leader hosted the US vice-president, who called on Russia to respect the September peace deal and withdraw its troops from Ukraine.
“Do what you agreed to do, Mr Putin,” Joe Biden said, accusing Moscow of a flagrant violation of international principles.
This year Russia has annexed Crimea from Ukraine and is accused of backing eastern separatists.
In Kyiv thousands came to mark the start of the protests which triggered these events.
The Maidan rallies eventually toppled Yanukovych but only after police snipers had killed around 100 demonstrators.
“We do not regret that the revolution took place. But we want the authorities to remember these guys who were shot here. We brought them to power, but they don’t do anything for us or the parents of these guys,” said one woman who came to pay her respects.
Many of the thousands cramming Independence Square are now scrutinising today’s government.
Euronews correspondent in Kyiv, Maria Korenyuk, said: “People who came to Maidan in November, 2013 demanded a total overhaul of the government. This year Ukrainians have got a new president and a new parliament. More than half the parliament has been changed. However, people are still waiting for radical reforms and the purging of officials. That’s why for many Ukrainians, the revolution hasn’t yet come to an end.”