Sens. Joseph Biden and Richard Lugar said Tuesday they will push bipartisan legislation this year that would triple humanitarian spending in Pakistan but threaten to cut military aid unless Islamabad does more to fight terrorists.

At a news conference, the two leaders of the Senate Foreign Relations Committee, said they worked closely with the State Department and USAID to draft the bill and believe it would be signed by President George W. Bush.

If the bill passes by year's end as the senators hope, it would send a sharp message to Pakistan that the U.S. is frustrated by continued terrorist activities along its Afghan border.

"While our bill envisions sustained cooperation with Pakistan for the long haul, it is not a blank check," said Lugar, the committee's top Republican.

The legislation would specifically authorize $7.5 billion to be spent in the next five years for development, such as building schools, roads and clinics. At the same time, the bill would withhold military assistance unless the State Department certifies Pakistan's security forces were making "concerted efforts" to go after al-Qaida and Taliban forces and not interfering in political or judicial matters.

Under the proposal, the president could waive this requirement in the interest of national security.

The U.S. has given Pakistan a total of $10.8 billion in economic and military aid since the Sept. 11 terrorist attacks, including some $5.6 billion to reimburse Islamabad for anti-terrorist operations. A recent independent audit concluded that there was little proof that the military aid had been used for that purpose.

Biden, chairman of the Foreign Relations Committee, said he supports giving the administration the chance to waive the military aid requirements "because the administration has acted in good faith" by expressing a willingness to change its policy toward Pakistan.

"This is a case where we're going to be spending a lot more money on economic aid than military," Biden, a Democrat, told reporters.

The Bush administration did not immediately provide comment. At a hearing in June, Assistant Secretary of State Richard Boucher said the administration was open to considering the approach.

President George W. Bush told reporters on Tuesday that there was "no question" that extremists are coming out of parts of Pakistan into Afghanistan and "that's troubling to us. It's troubling to Afghanistan, and it should be troubling to Pakistan."

Bush also said the U.S. will investigate Afghan President Hamid Karzai's charge that Pakistan's intelligence service was involved in a recent bombing in Kabul that killed dozens.