Brussels (AFP) - Russia has dropped its demands for a further delay in a landmark EU-Ukraine trade deal at the heart of the Ukraine crisis and accepts that it will now begin next year, the European Union said Monday.

"The reference that the (trade agreement) enter into force on 1 January 2016 was not contested by the Russian delegation," Trade Commissioner Cecilia Malmstroem said after talks with Russian and Ukrainian officials.

Malmstroem said there was a "clear understanding" that the deal would not be amended and would now be implemented on time.

Russian Economic Development Minister Alexei Ulyukayev had "made no threats of retaliation of any kind... and told the EU and Ukraine they could do as they wished," she added.

Diplomatic sources said last month that Russia was seeking a delay but that its request had not gone down well.

A joint statement after the meeting, attended also by Ukraine Foreign Minister Pavlo Klimkin, said the three sides would step up efforts to meet Russian concerns that its interests would suffer as a result of the trade pact, with officials due to report to ministers by July.

Russia had claimed that the so-called EU-Ukraine Deep and Comprehensive Free Trade Agreement will damage its own important economic ties and interests in the former Soviet state.

The free trade accord is part of the broader EU Association Agreement, whose sudden rejection by Kremlin-backed Ukrainian president Viktor Yanukovych in late 2013 triggered the protests that led to his downfall and the current crisis in Ukraine.

The deal was finally agreed in 2014 and was originally due to come into effect in January this year.

But in September the EU postponed implementation for a year to support peace efforts as a first ceasefire accord was negotiated in the Ukraine conflict between government forces and pro-Russian rebels.

In return, Russia promised to hold off on the retaliation it had threatened if the EU and Ukraine went ahead with the trade pact without resolving its concerns.

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Ulyukayev said Russia had not raised the question of delaying the trade pact and urged officials to use the remaining time as effectively as possible.

"I leave these talks feeling reasonably optimistic; there are signs that we understand each other," he was quoted as saying by the RIA Novosti news agency.

Several rounds of talks between EU, Ukraine and Russian officials had been held before but no progress was reported.

The EU still has tough sanctions in place against Russia over the Ukraine conflict.