The BBC's Chris Morris in Islamabad says that cross-border co-operation was high on the agenda when Mr Zardari and Mr Bush met at the UN.

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Top of the agenda was a meeting of the Shanghai Co-operation Organisation, a group that includes Central Asian nations.

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Also on the agenda will be Belgrade's level of co-operation with the International War Crimes Tribunal at the Hague and regional issues in southern Serbia, Kosovo and Montenegro.

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In May 2012 the EU and Turkey launched a "positive agenda", highlighting areas where they could expand co-operation.

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After the four-hour summit, Mr Cameron will travel to Paris to meet French President Francois Hollande at the Elysee Palace where co-operation on tax evasion and avoidance as well as tackling corporate secrecy will again be on the agenda.

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