US President Barack Obama has said Nato has agreed to his plans for a new, expanded missile defence system for Europe that would cover all Nato member countries and the US.
The US already has a missile defence system based mainly in North America and is planning one for its European allies.
President Obama spoke on the opening day of a Nato summit in Portugal. He said today's session would focus on the strategy for Afghanistan.
A top alliance official said Nato would begin reducing troops in Afghanistan in July and would end its combat role there by 2014 or earlier.
President Obama said the US and Nato partners had made “substantial progress” on the summit's first day.
The move heralds a fundamental shift in relations between the US and Russia.
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.
It is thought it will also allow passage of supplies through its territories as an alternative to a Pakistani route which has come under repeated Taliban attack.