UN Secretary General Ban Ki-moon was on Wednesday due to visit Pakistan, where he is expected to announce the launch of a UN probe into the assassination of former premier Benazir Bhutto.
His brief visit later in the day -- his first since taking office two years ago -- comes two days after gunmen kidnapped a top UN official in southwest Pakistan.
Pakistani officials say talks will focus on the expected formation of a UN commission to investigate the killing of Bhutto, a two-time prime minister who was killed at a campaign rally in December 2007.
"He's arriving in the afternoon. He will meet Prime Minister Yousuf Raza Gilani. Then he will call on President Asif Ali Zardari and attend a banquet before leaving for India tonight," a foreign ministry official told AFP.
"He is expected to announce the formation of a commission to investigate Benazir's killing," the official added.
Bhutto, the first woman to become prime minister of a Muslim country, was killed on December 27, 2007 in a gun and suicide attack after addressing an election rally in Rawalpindi, a garrison city near the capital Islamabad.
The Pakistani government at the time and US officials accused tribal warlord Baitullah Mehsud of plotting the attack, though he denies the charge.
Pakistan asked the UN to establish a commission to investigate the killing.
Last December, a spokesman for Ban said the UN leader hoped a commission could be established soon but that further consultation with Pakistan "was needed to examine the commission's structure, including its scope and mandate."
Ban has called for the "immediate and safe release" of John Solecki, the head of the UN refugee agency (UNHCR) in the city of Quetta who was snatched at gunpoint on Monday.
Pakistan condemned the "dastardly terrorist act" and launched a manhunt to find Solecki, but officials say they have no idea who was responsible. Criminal gangs, rebels and Islamist militants are known to operate in the area.