UK Foreign Secretary Jack Straw has met President Pervez Musharraf at the start of a three-day visit to Pakistan.
Mr Straw is expected to discuss the progress of talks with India
Counter-terrorism, nuclear arms, trade and peace with India featured in talks with the president, PM Shaukat Aziz and Foreign Minister Khurshid Kasuri.
Correspondents say soaring Afghan opium production is also likely to have been discussed. The UK says 70% of Britain's heroin is smuggled through Pakistan.
Mr Straw's Islamabad visit precedes talks in Afghanistan and India.
The BBC's Paul Anderson in Islamabad says that at the centre of the foreign secretary's packed agenda are what officials describe as the three Cs - counter-terrorism, counter-proliferation and counter-narcotics.
Mr Straw told a news conference he had "very substantial confidence" in the way Pakistan had handled the aftermath of the scandal involving disgraced scientist AQ Khan.
Dr Khan was pardoned last year after admitting transferring nuclear secrets to Iran, Libya and North Korea and is under virtual house arrest.
Pakistan says he will not be questioned by outsiders - including the UN nuclear watchdog.
The foreign secretary's talks in Pakistan came a day after Commonwealth ministers sharply criticised Gen Musharraf for breaking a promise to step down as army chief.
Mr Straw, however, said Britain was "delighted" that Pakistan had been fully readmitted to the Commonwealth.
"It is a very good sign of Pakistan's maturing as a democracy
and the recognition of the great leadership which President
Musharraf has shown during a difficult time for the world," he told state-run television.
On the war on terror, Mr Straw spoke warmly of Gen Musharraf's efforts - hundreds of al-Qaeda suspects have been arrested in Pakistan.
The Pakistani military has been hunting suspected al-Qaeda-linked militants in the unruly tribal region of South Waziristan bordering Afghanistan.
Osama Bin Laden is widely believed to be hiding in the area.
Mr Straw's Islamabad visit came a day before Indian Foreign Minister Natwar Singh is due to arrive for more peace talks.
The UK is a major foreign sponsor of the process, working behind the scenes to promote talks. Our correspondent says India and Pakistan have precious little to show for more than a year of negotiations.
But Mr Straw said Britain welcomed continued progress in the peace process, at the heart of which lies the dispute over the mountainous territory of Kashmir.
He said he saw a "good future" to the dialogue, adding: "What I look forward to ... is the border breaking down and so once again families which have been separated by that border being able to live in peace and harmony and security."