Brown reiterated Britain's pledge to invest 665 million pounds over four years in programmes aimed at tackling 'the root causes of extremism,' the spokesman said.

During his trip, Zardari is also appealing for western aid promises to be met - the international community pledged $5.7 billion of funding earlier this year but according to some reports only $300 million has been received.

Equally, Brown faces a delicate balancing act as he seeks to maintain Britain's ties with Pakistan while pressuring Zardari to accept US demands for more action against the Taliban.

Western leaders have tried to persuade Islamabad that it is the Taliban that is its enemy, not India.