There is a new chill in Russia's relations with the West, the BBC's James Rodgers reports from Moscow. He also considers whether the Kremlin's tough stance towards political opponents may be backfiring. His diary is published fortnightly.
A NEW COLD WAR?
"If the move towards our border continues, it will require measures of a military character," said the official, before going on to raise the prospect of a new arms race between Moscow and Washington.
We're not there yet. But if Russian rhetoric is strong off-the-record, it's pretty blunt in public too.
Diplomatic smiles: Russia had frosty things to say to Mr Gates
"We would like to hope, though I'm not optimistic, that in Washington politicians will pay attention to our concerns," Igor Ivanov, the Secretary of Russia's Security Council, said last week.
He was referring to Russian worries about US plans for a missile defence system to be sited in Poland and the Czech Republic. The United States sent Defense Secretary Robert Gates to Moscow to make Washington's case, and listen to the Kremlin's objections.
It's likely to be part of a long process. Nobody in Moscow seems to think that any good is likely to come of the new system. Despite Washington's contentions to the contrary, Russia is still concerned that the missile shield could represent a threat to its security.
Even if there hasn't been a return to the Cold War, or a new arms race, there is a sense of frustration with the United States which has its roots in the 1990s, and the aftermath of the collapse of the Soviet Union.
Nato's decision to take in countries of the former Soviet bloc, and even of the former Soviet Union, left many Russians feeling cheated. Many people here see Nato as a Cold War-era institution which should have ceased to exist once the stand-off ended.
Moscow says its interests should be understood. Many here clearly feel that Washington isn't listening.
No-one in Russia expects an immediate confrontation. The Cold War belonged to different times. Two ideological adversaries faced off, backed by massive military force. Today, that ideological rivalry has gone. But the two foes who became friends - in name at least - during the 1990s are now looking at each other in a different, harsher, light.
As the official I quoted at the beginning rather sarcastically put it: "In the Cold War, we had mutual understanding and mutual respect. Now we're experiencing the disadvantages of being an ally and a partner."
It's one of the ongoing challenges of foreign reporting. You get to know a country which isn't your own, and you write about it. You always have to try, to some extent, to look at it through the eyes of the people you are reporting to: never allowing your familiarity either to breed contempt, or lead you to adopt unquestioningly the conventional wisdom of the country you're living in.
You always have to ask yourself why people should care - what constitutes a real story?
Garry Kasparov (centre) says the authorities have overreacted
When 3,000 people turn out in central Moscow for a protest march, it doesn't necessarily pass the test.
When thousands of riot police patrol the streets of the Russian capital, it does.
The former world chess champion turned political activist, Garry Kasparov, has landed himself in trouble with Russia's Federal Security Service (FSB) - the main successor to the Soviet-era secret police, the KGB.
His interrogation on Friday, like the demonstration he organised in Moscow the weekend before, guaranteed press interest in his protest against President Putin.
The huge deployment of security forces to prevent the "March of the Dissenters" from going guaranteed the Kremlin's critics much wider media coverage than they could otherwise have dreamed of.
Mr Kasparov was one of the march's organisers. Two days before it was due to take place, he had expressed the hope that 5-7,000 people would turn out. The coalition he has put together, "Another Russia", draws on groups from across the political spectrum.
The movement is still finding its feet. Given the security forces' huge presence, it's reasonable to accept activists' claims that some people were prevented from getting there, or too scared to try. Nevertheless, 5-7,000 people in a city of 10 million, and a country of almost 150 million, hardly constitutes critical mass.
What are the authorities here so afraid of?
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