On the first of two days of informal talks, starting in Oslo, Norway around 1030 GMT, Secretary of State Condoleezza Rice will defend the US plan to erect its "star wars" style shield in Poland and the Czech Republic.
Moscow claims the shield, due to be in operation by 2013, could upset the strategic balance or start an arms race, and it disputes US claims that "rogue states" like Iran could soon develop missiles capable of reaching Europe.
In line with its heightened rhetoric on other issues, like energy or the possible use of its UN Security Council veto over Kosovo, Russia has reacted testily to a US offer of missile and other military cooperation.
"What we see in the American offer are several aims which do not address the principal, that is a joint analysis of the threat," said Russian Foreign Minister Sergei Lavrov, who will confont the NATO allies around 1600 GMT.
Apart from doubting Iran’s ability to be able to launch warheads into Europe in the next decade, Russia is concerned the shield will grow beyond the 10 planned interceptors in Poland and a tracking radar in the Czech Republic.
"We know from experience that when you have a system it keeps developing, it cannot stop," Russia’s ambassador to NATO, Konstantin Totsky, warned last week.
Washington also has some convincing to do among its NATO allies.
While they agree that Iran, and to a lesser extent North Korea, do indeed pose a potential missile threat, they are concerned that the shield’s new footprint will not cover all of members Bulgaria, Greece, Romania and Turkey.
To protect them, the alliance is considering whether it could "bolt on" its planned theatre missile defences — a short to medium range system normally used to protect troops and still in testing — to the US system.
On the eve of the meeting, Rice expressed confidence that both Europe and the Russians could be convinced the shield is in their interests given the potential proliferation of ballistic missiles and weapons of mass destruction.
"It’s simply not possible that this could be considered a system that could in any way threaten the Russian strategic deterrent, it’s just not capable of doing so," she told reporters travelling with her to Oslo.
All 26 allies will also want to deliver a strong message to Russia about the need for a quick decision at the Security Council on Kosovo’s status, almost certainly a form of internationally-supervised independence.
NATO launched a bombing campaign against Serbia in 1999 to stop Belgrade cleansing the province of its separatist minded ethnic Albanian majority, and the alliance still has some 17,000 troops based there.
With the ethnic Albanians impatient to breakaway, NATO fears that its troops could get sucked into any violence that develops as the political process over Kosovo’s future drags on.
Russia, a strong ally of Serbia, rejects the notion that independence should be imposed on a province Belgrade considers an integral part of its territory, as it could encourage separatists elsewhere, such as in the restive Caucasus.
Separately, the ministers will assess progress in Afghanistan — NATO’s biggest and most ambitious operation ever — amid signs that an expected spring offensive by Taliban rebels has not been as strong as first feared.
No new calls for reinforcements are expected, and Rice said talks would focus on "the need for better coordination between civilian and military activity … as well as looking at how we can continue to seek and receive contributions to the war effort."