Joe Biden, the US vice president, has arrived in Islamabad, the capital of Pakistan, for talks with the country's president, Asif Ali Zardari, and senior government officials. Earlier in the day, a suspected US drone attack killed at least four people in Pakistan's tribal North Waziristan region.
Biden's trip comes after two days in Kabul, where he said that Pakistan needed to do more to help the US in its battle against Taliban and other fighters in Afghanistan.
Al Jazeera's Kamal Hyder, reporting from Islamabad, said that Biden would also meet with General Ashfaq Kayani, the chief of the army, and Yousuf Raza Gilani, Pakistan's prime minister.
"Biden is said to be carrying an important message from the Obama administration and is likely to discuss US concerns that the Pakistani government has performed miserably on the economy and political uncertainty," our correspondent said.
"Due to security concerns, American marines will be providing security to the US vice president after the Punjab governor's assassination."
Salman Taseer, the governor of Pakistan's Punjab province, was killed earlier this month in Islamabad's Kohsar market, an area popular with wealthy Pakistanis and expatriates.
'More pressure'
Barack Obama, the US president, and other American officials have criticised Pakistan for not doing enough to curb fighters within its borders who attack US-led forces in neighbouring Afghanistan.
"It's going to require more pressure - more pressure on the Taliban, from Pakistan's side of the border, than we've been - we've been able to exert so far," Biden said at a joint news conference with Afghan President Hamid Karzai.
"There are many hard days that lie ahead."
The US-Pakistan relationship has been strained recently with Pakistan complaining that Washington does not provide adequate support and does not understand its intricate security needs.
Drone attacks
Also on Wednesday, a suspected US drone attack killed several people in Pakistan's North Waziristan tribal district.
Most of the estimated 100 missile attacks last year inside Pakistan have taken place in North Waziristan, a tribal area effectively under the control of Taliban and al-Qaeda fighters.
Pakistani officials protest the missile strikes by US drones, but they are believed to have secretly authorised at least some of them.
The missile attacks have been credited with killing many top ranking fighters, but they have also stirred public anger in Pakistan due to the high numbers of civilian casualties.
