The 1945 Yalta conference: High water mark of the last alliance

President Putin was the first foreign leader to call Mr Bush after the attacks on New York and Washington, and has done almost everything possible to back his war against terrorism, short of offering direct military involvement.

But a lot now depends on the next meeting between the two leaders at Mr Bush's ranch in Texas next month, where a big effort will be made to overcome the biggest thorn in the side of US-Russian friendship: Washington's plans for a missile defence shield, and its consequent need to modify or withdraw from the 1972 Anti-Ballistic Missile (ABM) Treaty.

Mr Putin said after Sunday's meeting that there remained a lot of work to do before the Texas summit, but he said progress had been made.

US officials have been working on the details of a new package of major cuts to strategic arsenals, which Russia has hinted would help it to accept changes to the ABM treaty.

Potential backlash

However if anything goes wrong, and the US resorts to unilateral withdrawal from the treaty - a move it could take by January - the sea change in relations could move into reverse, with hawkish conservatives on both sides regaining the influence they currently appear to have lost.

In the aftermath of the US attacks, Russia's longstanding resentment of US global dominance, expressed in calls for a "multipolar world" - or effectively a coalition to challenge US hegemony - appears to have evaporated.

Defence Secretary Donald Rumsfeld is a strong supporter of missile defence

This would normally have been a prominent theme at any meeting between Mr Putin and the Chinese leader Jiang Zemin.

But while they called for a quick end to the fighting in Afghanistan after talks on Saturday, and reaffirmed their commitment to the ABM treaty, they also urged all nations to join the US-led coalition against terrorism.

Russia's assistance to the US consists so far in:

• Providing intelligence, for example on systems of caves and tunnels in Afghanistan where Osama Bin Laden may be hiding
• Encouraging Central Asian states to assist US troops
• Promising to arm the Northern Alliance
• Allowing use of its airspace for humanitarian purposes
• Suggesting that Russian forces could conduct search and rescue operations in Afghanistan
• Offering medicines and vaccines to help the US fight anthrax

Tests of the missile system have had mixed results

If agreement can be reached over the ABM treaty and Nato, the two biggest potential clouds on the US-Russian horizon are possible further moves in the war on terrorism itself.

It would currently be difficult for Russia to reconcile itself with US attacks on Iraq, or to the idea of a permanent US military presence in Central Asia.

But these moves do not appear to be imminent, and with the speed that attitudes are changing in the Kremlin it is impossible to say how Russia would respond to them a year or two years down the line.