By Rupert Wingfield-Hayes
BBC News, Moscow
Russia and the US remain far apart after talks in Moscow
It is not unusual for senior diplomats to disagree. It is, however, extremely unusual to see them do so as obviously and as publicly as the Russians and the Americans have done in Moscow.
As Condoleezza Rice and her Russian counterpart, Sergei Lavrov, sat down to face the world's media you could have cut the atmosphere with a knife.
Two of the world's most experienced diplomats stared straight ahead, stony faced, barely acknowledging the other's existence.
Mr Lavrov was the first to speak and he did not pull his punches.
He made it painfully clear that the talks had achieved nothing, and demanded that the United States immediately freeze its plans to deploy a missile defence system in Eastern Europe.
When her time came, Condoleezza Rice did her best to sound much more conciliatory.
Ever the diplomat, she insisted the discussions had been constructive, and that in general US-Russian relations were still in a much better state than they were in the bad old days of the Cold War.
But it was all too obvious that Ms Rice was trying rather too hard to sound upbeat, and that the talks had been a disaster.
The only thing the two sides appeared to agree on was that they had talked, and that they should continue to do so in the future.
Mr Putin wants to continue to dominate the political system
It is hard not to draw the conclusion that Russian-US relations are now at their lowest point since the end of the Cold War.
The biggest single cause is the now notorious US missile defence system.
At one level, Moscow simply does not trust the United States when it says the system is no threat to Russia.
The system consists of a high-powered radar, to be established in the Czech Republic, and a group of interceptor missiles, which will be based in Poland.
Washington says the system is designed to shoot down conventional or nuclear tipped missiles fired by "rogue states" towards Europe. For "rogue state" read Iran.
Russia, not unreasonably, points out that Iran does not presently possess the long range missile technology, or nuclear warheads, the system is designed to protect against.
From Moscow's point of view there is no need to deploy a system to defend against a threat that, so far, does not exist.
On another level, Moscow is extremely angry that the United States has chosen to base its new missile system in two countries that were once part of the Warsaw Pact.
Russian defence experts say that in the mid-1990s Washington made a promise to Moscow that, following the collapse of the Soviet Union, it would not push its military deployment up to the borders of the old Soviet empire. The US, they say, is breaking its word.
Levers of power
But there is another dimension to this argument that should not be forgotten. That is the domestic dimension. In Russia these are nervous days.
In five months time, Mr Putin must step down as president after eight years. In recent weeks he has made it increasingly clear that he intends to stay on in power, perhaps as Russia's prime minister, perhaps in some other capacity.
If Mr Putin wants to continue to dominate Russia's political system, he must continue to control the levers of power.
To do that he needs to be able to change the constitution, and to do that he needs his party, United Russia, to win a two-thirds majority in December's parliamentary elections.
One sure-fire way of drumming up support for himself, and his party, is to have a fight with the United States.