Former Soviet leader Mikhail Gorbachev has accused the West of "provoking Russia" and said the USSR collapsed in 1991 because of "treachery".

The BBC's Steve Rosenberg in Moscow was given a rare interview with him, 25 years after the USSR's demise.

Mikhail Gorbachev, 85, has been having health problems. But his sense of humour is indestructible.

When we meet he points to his walking stick. "Look", he says, "now I need three legs to get around!"

Mr Gorbachev agreed to talk to me about the moment the world changed: the day the Soviet superpower fell apart.

"What happened to the USSR was my drama," he tells me. "And a drama for everyone who lived in the Soviet Union."

On 21 December 1991, the evening news bulletin on Russian TV began with a dramatic announcement: "Good evening. This is the news. The USSR no longer exists…"

A few days earlier, the leaders of Russia, Belorussia and Ukraine had met to dissolve the Soviet Union and form a Commonwealth of Independent States. Now, eight other Soviet republics had decided to join them.

Together they had defied Mikhail Gorbachev: the Soviet leader had been struggling to keep the republics together in a single state.

"Behind our backs there was treachery. Behind my back," Mr Gorbachev tells me. "They were burning down the whole house just to light a cigarette. Just to get power. They couldn't get it through democratic means. So they committed a crime. It was a coup."

On 25 December 1991, Mikhail Gorbachev announced his resignation as Soviet president. At the Kremlin, the Soviet flag was lowered for the last time.

"We were well on the way to a civil war and I wanted to avoid that," Mr Gorbachev recalls.

"A split in society and a struggle in a country like ours, overflowing with weapons, including nuclear ones, could have left so many people dead and caused such destruction. I could not let that happen just to cling on to power. Stepping down was my victory."

In his resignation speech, Mr Gorbachev claimed that, as a result of his perestroika reform programme, society "had acquired freedom". Twenty-five years on, I ask him whether he thinks that freedom is under threat in today's Russia.

"This process hasn't been completed," he replies. "We need to speak frankly about this. There are some people for whom freedom is an annoyance. They don't feel good with it."

"Do you mean Vladimir Putin?" I ask.

"You'll have to guess who I mean," he replies. "This is one question I'll leave you to answer."

In our conversation, Mikhail Gorbachev avoids direct criticism of Vladimir Putin. But he drops several hints that he and President Putin have their differences.

"Does Putin ever ask your advice?" I ask.

"He knows everything already," replies Mr Gorbachev. "Everybody likes to do things their own way. C'est la vie, as the French say."

The former Soviet president is scathing of modern Russia. "Bureaucrats," he tells me, "stole the nation's riches and began to create corporations".

He criticises one of President Putin's closest associates, Igor Sechin, head of the oil giant Rosneft, accusing him of trying to influence affairs of state.

He attacks the West, too, accusing it of "provoking Russia".

"I'm sure that the Western press - and that includes you - has been given special instructions to discredit Putin and get rid of him. Not physically. Just to make sure he steps aside. But, as a result, his popularity rating here has reached 86%. Soon, it will be 120%!"

It was Mikhail Gorbachev's warm relationship with the late US President Ronald Reagan that paved the way for the end of the Cold War. So what does Mr Gorbachev think about the new man heading for the White House? Has he ever met Donald Trump?

"I've seen his high-rise buildings, but I haven't had the chance to meet him in person, so I cannot judge his views and policies," Mr Gorbachev tells me. "But it's an interesting situation. In Russia everyone thought the Democrats would win - me included, although I didn't say it."

In the West, many people view Mikhail Gorbachev as a hero: as the man who gave freedom to Eastern Europe and allowed the reunification of Germany. But to many in his homeland, Mr Gorbachev is the leader who lost their empire.

Mikhail Gorbachev - key dates:

1931- Born in Privolye, a rural area in Stavropol, southern Russia

1955- Graduates from Moscow State University law school, member of Communist Party (CP)

1970- CP First Secretary in Stavropol

1980- Full member of Soviet CP Politburo

1985- Politburo elects him General Secretary of CP

1987-1989- Pushes through far-reaching reforms, called "glasnost" (openness) and "perestroika" (restructuring)

1987- Signs major nuclear disarmament treaty with US

1990- Agrees to reunification of Germany after fall of Berlin Wall in 1989

1991- Detained during abortive coup by Soviet hardliners in August, then resigns in December

"Do you accept any responsibility for the fall of the USSR?" I ask him.

"What upsets me is that, in Russia, people don't sufficiently understand what I set out to achieve and what I actually did," he says.

"For the country, and for the world, perestroika opened the way to co-operation and peace. I'm only sorry I was unable to see it through to the end."

At the end of the interview, Mikhail Gorbachev and I move over to his piano. I play and Mr Gorbachev sings some of his favourite Soviet hits.

These impromptu singsongs have become a curious but lovely tradition after a Gorbachev interview. The man who changed the world with perestroika loves to croon.

"Between the past and the future is the blink of an eye," he sings, "and that instant is what we call life."

The Soviet Union passed in the blink of an eye. What are 70 years compared to the Roman or Ottoman empires?

But I believe it is unfair to blame Mr Gorbachev - or the breakaway republics - for destroying the Soviet empire.

The USSR may have been flawed from the start: economically, politically and ideologically. Perhaps this was fated to be a short-lived superpower.