A historic deal which will bring the US and its Western allies together with Russia to produce a nuclear missile shield for Europe is due to be agreed at the Nato conference in Lisbon.
Plans for the shield were agreed by Nato members last night, but the landmark involvement of Russia heralds a fundamental shift in relations between the two former adversaries. As well as missile defence, Moscow is expected to agree to Nato's request for assistance in the Afghan war, with the supply of helicopters and allowing passage of supplies through its territories for the International Security Assistance Force (Isaf) as an alternative to a Pakistani route which has come under repeated attack.
Nato officials said Russian President Dimitry Medvedev was very likely to accept the invitation to join the missile shield programme. But Nato Secretary-General Anders Fogh Rasmussen warned that Republican opposition in the US to the Start nuclear warhead reduction treaty would have damaging consequences. "I would strongly regret if that is the case and ratification is delayed," he said.
The setting up of the ballistic defence system, estimated to cost €200m, was expected to be ratified by the 28 Nato member states, along with an offer of co-operation made to the Russian delegation led by Mr Medvedev.
Senior Russian officials indicated last night that the offer was likely to be taken up. Sergey Prikhodko, an aide to Mr Medvedev, said: "The idea of a joint missile defence is real. The process is quite simple. The issue is purely practical and its implementation may be carried even in the short-term perspective, rather than a long-term one, given that the sides have political will."
The defence shield bringing the West and Russia together is remarkable, as the issue was a source of friction when the Bush administration planned to site missiles in Poland and the Czech Republic.
President Barack Obama scrapped that plan on getting to the White House, and the aim now is to initially have the main "hardware" on US warships in the Mediterranean while land locations are explored.
The system will be developed over a 10-year period, with Britain contributing the early warning radar station at Fylingdales and the data processing centre at Menwith Hill – both part of the existing US defence system – to the programme.
Moscow is now believed to be seeking further concessions in return for helping in Afghanistan and for agreeing to involvement in the nuclear shield programme.
Russian forces remain in South Ossetia and Abkhazia two years after the war with Georgia, which is a Nato member. Sergey Lavrov, the Russian Foreign Minister, is said to have asked Nato to desist from deploying "significant military forces" to countries which joined Nato after the break-up of the Soviet Union in 1991, saying their presence would not be conducive to a relationship of trust.
Political developments in the US may add to pressure on the rapprochement between the West and Russia. Just one Senate Republican has declared support for the START treaty with Russia, and last week the leading Republican negotiator, John Kyl, said too many issues remained unresolved to allow a vote this year.
Sergei Rogov, the head of the Moscow-based USA and Canada Institute, warned: "The failure to ratify the treaty will deal a very painful blow to Obama's administration"
The system is meant to counter threats from so-called rogue states, but Turkey opposed naming Iran, a fellow Muslim nation, in a communiqué planned by the Alliance.
But Mr Rasmussen said: "More than 30 countries already have, or are aspiring to acquire, missile technologies which can hit Nato territory, so there is no need to name a particular country."