BERLIN (AFP) - German Chancellor Angela Merkel will visit Russia's Vladimir Putin in Moscow in the twilight of her reign on Friday (Aug 20), with Afghanistan set to be the final twist in their long and thorny relationship.

From alleged cyberattacks to the conflicts in Ukraine and Syria, Mrs Merkel and Mr Putin have rarely seen eye to eye during the chancellor's 16 years in power.

Her return to Moscow for what is likely a farewell visit comes on the anniversary of the poisoning of Kremlin critic Alexei Navalny - which sent relations plunging to a new low as Germany pinned the blame on Russia.

Now, as Mrs Merkel prepares to bow out of politics following an election in Germany on September 26, the crisis in Afghanistan could be the latest subject to drive a wedge between the two leaders.

While Mrs Merkel has described the Taliban's return to power as "bitter", Russia has taken a more conciliatory tone.

Moscow is seeking contact with the Taliban, with top diplomat Sergei Lavrov calling it a "positive signal" that the Islamists are "declaring and in practice showing their readiness to respect the opinion of others".

The trip will be the 20th visit to Russia for Mrs Merkel, a Russian speaker who grew up behind the Iron Curtain in the former communist East Germany.

German government spokesman Steffen Seibert said Afghanistan would "obviously" be up for discussion, along with Ukraine.

Ukraine assurances

The German leader will also travel to Ukraine on Sunday, where she will meet President Volodymyr Zelensky amid continued tensions over Moscow's troop build-up on Ukraine's borders.

Efforts to secure peace in Ukraine have been one of Mrs Merkel's flagship projects and she will want to avoid creating the impression that the peace process has "become a political zombie", Mr Fyodor Lukyanov, editor-in-chief of the Russia in Global Affairs magazine, told AFP.

Mrs Merkel may also seek to provide Ukraine with assurances over Nord Stream 2, the controversial gas pipeline set to double natural gas supplies from Russia to Germany.

The pipeline had been delayed due to objections from several EU countries and the United States for bypassing Ukraine's gas infrastructure, depriving the nation of badly needed transit fees.

But the United States and Germany struck a deal in July to allow its completion, including a promise of sanctions on Russia should it use energy as a weapon against Ukraine.

Mr Seibert said the "still unresolved" Navalny case would also feature during talks on Friday and had placed a "heavy burden on the relationship with Russia".

The Kremlin critic was treated in a Berlin hospital after mysteriously collapsing on an internal Russian flight last year, and was jailed when he returned to Russia in January.

To mark the Navalny anniversary, the Kremlin on Wednesday accused the German government of a "propaganda campaign" against Russia and said Berlin was "interfering in the internal affairs of our country".

Mr Navalny, meanwhile, dictated an explosive letter from prison in which he called on global leaders to stamp out corruption and impose sanctions on members of Mr Putin's entourage.

Other points of contention have included alleged espionage and cyber attacks, with Mrs Merkel declaring she was personally targeted by Russian hackers.

In a particularly dramatic case, a Georgian of Chechen origin was shot dead in broad daylight by a passing cyclist in a park in Berlin - a murder that Germany has accused Moscow of orchestrating.

And just last week, a British man named as David S. was arrested on suspicion of spying for Russia in exchange for cash while working at the British embassy in Berlin.

'I trust her'

But despite the many tensions, Mrs Merkel has always sought to maintain a dialogue with Putin.

Mr Lukyanov predicts that Mr Putin will give Mrs Merkel a "warm reception".

"In a way, Mrs Merkel is close to him. The two of them have been through so much together," he said.

In previous meetings, the Russian leader has sought to charm the chancellor by giving her flowers or helping her into her coat.

But he also invited his huge black labrador Konni to a meeting in 2007 - hardly a welcome gesture for Mrs Merkel, who has admitted being nervous around dogs.

"I trust her, she is a very open person," Mr Putin has said of Mrs Merkel.

The chancellor is not known to have made similar remarks about Putin.