White House upbeat after 'unique' summit

The two presidents ended their summit with a 50-minute walk in the grounds of this lush estate, talking one to one, with only interpreters present.

President Obama's National Security Advisor Tom Donilon repeatedly used a single word to describe the meeting - "unique".

Its importance, he said, was that it came so early in President Xi's term of office, that it was so informal and that it added up to a lengthy eight hours of talks covering just about every subject of interest in great depth and breadth.

In the first session the two men set out their visions for their country and their strategic aims.

Over dinner there was a lengthy discussion of security and in particular North Korea.

The final session was on economics and cyber security.

This is the most awkward subject for the two men. President Obama told President Xi that the cyber attacks from "Chinese entities" amounted to theft of business and military secrets.

If they continued it would inhibit the economic relationship between China and the US reaching its full potential. American sources say President Xi said he would investigate.

'Shared threat analysis'

The White House says the talks on North Korea ended with a full agreement on the goal of a denuclearised peninsular.

Tom Donilon said that the important point was that both powers had a "shared threat analysis" and recognised that a nuclear North Korea would up-end security in the region, with a profound effect.

President Obama also warned that the growing problems over disputed islands in the pacific should be "de-escalated" and resolved through diplomatic means, not actions.

Perhaps none of this sounds very much, and perhaps it won't amount to much.

But it was interesting that Tom Donilon - who is coming to the end of his term as national security adviser and who has been deeply involved in the whole pivot to Asia - sounded so upbeat and enthusiastic about the meeting.

He set out the real purpose - to push back against the suggestion that there is an inexorable dynamic between a rising power and an established power, one that leads to clashes and conflict sometime in the future.

It perhaps sounds overly dramatic to suggest the purpose of the Sunnylands summit was to avoid World War III, but it is certainly aimed at making sure both sides know the flashpoints, and talk about them, long before disagreements degenerate into something worse.