MOSCOW: Russian President Vladimir Putin and US President Donald Trump discussed the possibility of a referendum in separatist-leaning eastern Ukraine during their Helsinki summit, Russia’s ambassador to the US said Friday.

Ambassador Anatoly Antonov revealed the discussions amid confusion and concern in the US about what the two world leaders actually agreed upon behind closed doors.

“This issue (of a referendum) was discussed,” he said, adding that Putin made “concrete proposals” to Trump on solutions for the four-year, Russian-backed insurgency in eastern Ukraine, which has killed more than 10,000 people.

He did not elaborate on what Putin’s solutions would be.

The move may be seen as an effort to sidestep European peace efforts for Ukraine and increase the pressure on the Ukrainian government in its protracted conflict with pro-Russian separatists in the Donbass region.

Trump tweeted that the two men discussed Ukraine, but has not mentioned a referendum or revealed specifics.

The US and Russia have been on opposing sides of the conflict in Ukraine, which was unleashed after a popular uprising in 2014 against Ukraine’s pro-Russian president and Russia’s retaliatory annexation of Ukraine’s Crimean Peninsula a month later.

Ukraine’s government didn’t immediately respond to the developments but former Foreign Minister Konstantin Grishchenko said, “Kiev will never agree to a referendum in the Donbass initiated by Russia.”

“The Kremlin already used a referendum as justification for annexing Crimea. And Moscow is trying to use this theory and spread it to the Donbass,” he said on the 112.ua television network.

International powers did not recognise the Crimean referendum that preceded Russia’s annexation. Ukraine’s Donetsk and Luhansk regions also held referendums in 2014 that were not recognised by Ukraine’s government.

European powers are also expected to oppose a referendum in the Donbass, where pro-Russian separatists hold sway. They have been committed to a 2015 peace deal signed in the Belarusian capital of Minsk that has helped reduce the fighting but failed to find a lasting political solution for the region.