This is Mr Gilani's first visit to US after taking over as prime minister
The Pakistani Prime Minister, Yousuf Raza Gilani, is in Washington preparing for talks with President Bush and senior officials.
The trip comes amid intensifying US pressure on Pakistan to move against Taleban and al-Qaeda militants.
This is Mr Gilani's first visit to the United States since he took power after February's elections.
He is also expected to meet the Democratic and Republican presidential hopefuls, Barack Obama and John McCain.
Pakistan is a strategic ally of the United States in its war against terror.
US and Afghan officials say Taleban and al-Qaeda militants have established their strongholds on Pakistan's western border from where they carry out attacks into Afghanistan.
"It is in the interest of Pakistan to curb extremism and terrorism," Mr Gilani told reporters before leaving for the US.
Mr Gilani can expect to hear some tough words in Washington, says the BBC's Kim Ghattas in Washington.
President Bush will press him on the need to do more to fight the militants in the tribal areas near the Afghan border when he meets him on Monday, our correspondent says. Mr Gilani is due to spend three days in the US.
The Pakistani prime minister is also scheduled to meet senior US officials, including Secretary of State Condoleezza Rice and Defence Secretary Robert Gates.
In recent months the US and its allies have pledged hundreds of millions of dollars in military and other forms of assistance to help Pakistan's new government tackle militancy in border areas.
Earlier this month, Mr Gates said he was considering sending additional troops to Afghanistan to counter the flow of insurgents from Pakistan.
Washington has also said it is concerned about peace deals that Islamabad has been signing with some of the radical groups in its western tribal-dominated areas.
The Pakistani government says the peace deals will bring stability to the volatile regions.
But Washington argues this gives the militants too much room to manoeuvre and increases the threat to Nato troops across the border.
US military commanders have warned that if there is ever another attack against the US, it will be planned in those areas.
But there will be statements of support - and possibly action - to back them as the US seems keen to encourage the fragile transition from military to civilian rule in Islamabad, our correspondent says.
Last week, President Bush announced that he wanted to allow Pakistan to upgrade its F-16 fighter jets by using two-thirds of the annual counter-terrorism aid it gets from the US.
But the US Congress has criticised the move, saying the jets are not essential to the fight against the militants in the tribal areas.