German chancellor Angela Merkel’s top aide on Russia has said she is “frustrated” by Moscow’s broken promises, while raising the alarm on Russian air manoeuvres.

Gernot Erler spoke to Polish daily Gazeta Wyborcza on Monday (8 December), ahead of new Russia-Ukraine peace talks due in Minsk on Tuesday.

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“What we are seeing is the chancellor’s growing frustration with the Russian president. Vladimir Putin has promised her a lot, but so far he hasn’t kept his word. That was the case, for instance, with the ceasefire accord negotiated [in Minsk] in September”, he said.

“I'm also frustrated. I never thought the Russians were ready to destroy everything that we'd achieved”, he added.

“We treated Russia as a partner … in vain. There is no way to return to those times”.

Delegates from Russia, Ukraine, two self-proclaimed republics in east Ukraine, and the OSCE, a European multilateral body, are to meet on Tuesday in Minsk to try to revive the 5 September ceasefire accord.

Opinion is divided on whether Putin intends to freeze the conflict, or to launch a new offensive against the city of Mariupol in south-east Ukraine, establishing a land-bridge to Crimea, which he annexed in March.

But the West has accused him of violating the extant Minsk ceasefire pact by pouring fighters and armour into Ukraine and by letting rebels under his control continue to wage war.

Erler, a 70-year old Russia veteran, was the mastermind of the EU-Russia “Partnership for Modernisation”, launched in 2010.

He said the West should leave Crimea to one side and focus on stopping the fighting in east Ukraine.

He also promoted plans for new trade consultations between the EU and Russia’s economic bloc, the Eurasian Customs Union, as a way of reducing tensions.

He told the Polish daily that EU sanctions are having a smaller effect on the Russian economy than the slump in oil prices.

“It [Russia] still has sufficient currency reserves [to prevent an economic crisis]. The sanctions are not making a big impression".

But he noted the Kremlin is surprised it hasn’t managed to split the EU on its sanctions regime.

“Russia can’t understand it. Our show of unity is having a greater effect than the sanctions per se”.

“Putin’s recent decision to halt the construction of South Stream [a gas pipeline from Russia to Italy] was an attempt to sow discord. Bulgaria, Hungary, and Serbia - countries which are, to say the least, very accommodating to Russia - will suffer the most from this decision. So maybe the whole point is to mobilise them against Europe’s joint policy”, Erler noted.

“Big businesses [in the EU] have lobbied governments from the beginning [of the crisis]. But they’ve been told that, in this case, politics takes precedence over economic interests. They respect that now. Europe will speak to Russia with one voice”.

Erler defended Nato's decision not to build new bases on Russia’s border, saying this would have broken previous Nato-Russia accords.

“Even though Russia has violated international treaties, we shouldn't do the same”, he said.

'All it takes is one mistake'

But he voiced concern over a Russian campaign, which began in March and which escalated after a Nato summit in September, of harassing Nato air and naval assets.

A recent survey by the London-based think tank ELN said Russian operations have already caused 12 “serious incidents” which almost ended in loss of life.

In one event, on 3 March, a Russian plane which had concealed its position almost crashed into a Swedish passenger jet over Malmo, foreshadowing the Malaysia Airlines disaster in July.

Last weekend, a squadron of 24 Russian bombers and transport planes approached Lithuanian airspace, putting the Lithuanian army on alert.

For its part, the European Commission has tasked the European Aviation Safety Agency (Easa) in Cologne, Germany, with doing a study on how to protect civilian flights.

It will work on “further identifying appropriate solutions and follow-up measures to address such events at the European level”, Easa said on Monday.

“This process of spiralling tensions is very worrying”, Erler told Gazeta Wyborcza, echoing the ELN's earlier warning that accidental loss of life could lead to a military response by either side.

“We don’t know where it might lead us. We have to be very careful. All it takes is for one soldier to make a mistake”.