By Jonathan Marcus BBC defence correspondent

The Nato Secretary General, Lord Robertson, does not look much like a revolutionary, but his aim is to help shape a radical transformation of the Atlantic Alliance to ensure that it remains relevant amidst the geo-political disorder of the 21st Century.

If all goes according to plan, by the end of this year Nato will have established a new relationship with Russia, and it will have agreed to what will probably be the largest single intake of new members in its history.

But Lord Robertson's ambitions go further.

While insisting that Nato still plays a key role in security matters, he has sounded increasingly defensive as he has sought to downplay suggestions that the war in Afghanistan has left the Alliance very much on the sidelines.

New agenda

The Secretary General, with the backing of most of the alliance's major players, wants to transform Nato's agenda to focus more on pressing threats, like international terrorism and the spread of weapons of mass destruction.

Nato and Russia will co-operate in matters of security

These are both issues that are likely to figure on the agenda of the new Nato-Russia council, a symbolic fresh start between the alliance and Moscow, intended to capitalise on the new mood of co-operation in the wake of the attacks on the World Trade Center and the Pentagon last September.

A Nato-Russia summit is planned for Rome at the end of this month to launch the new forum, and the aim is to have the new structures up and running well before the Prague Nato summit in November.

This is not least because the alliance's next batch of new members could well include one or more of the three Baltic republics, the first time that Nato will have extended its borders to take in former Soviet territory.

Nobody is taking odds as to how many of the nine or so candidate countries may actually be asked to join, but there is a chance that up to seven - Slovenia, Slovakia, the three Baltic republics, and Romania and Bulgaria - might just squeeze in.

Military challenges

This highlights the importance of what appears the most mundane element of Lord Robertson's proposals, an overhaul of the way Nato does its business, how meetings are organised and so on.

But if the bureaucracy needs modernising so too does Nato's military capability.

Existing efforts to improve capabilities have had mixed results.

Nato now wants to define a much narrower range of targets, which may well involve some of its smaller members pooling capabilities or giving up some categories of military activity altogether.