Prime Minister Gordon Brown is holding talks with Pakistan President Asif Ali Zardari, with the fight against the Taliban high on the agenda.
Britain and its allies fighting in Afghanistan want maximum co-operation from Islamabad in controlling the border regions between the two countries.
Mr Brown recently renewed his warning that three-quarters of terrorist plots against Britain come from the area, where Pakistani security forces recently fought off Taliban incursions.
Mr Zardari will be at 10 Downing Street as part of a three-day trip to the UK, one of a number of visits to this country he has made since taking power two years ago.
When the pair last met, in May, Mr Brown praised Pakistan's efforts, promised aid for those displaced by the fighting and reaffirmed his commitment to a "new strategic dialogue" with Islamabad.
A Downing Street spokesman said they would discuss a number of regional issues including Afghanistan.
