A senior White House official says the United States is trying to enlist Pakistan in its war on terrorism and has made specific requests for help.

This official indicates the Bush administration has asked Pakistan to close its border with neighboring Afghanistan.

A diplomatic push obviously intensified after Pakistan's President Pervez Musharaff promised his cooperation in the war on terrorism.

Within hours, Secretary of State Colin Powell called President Musharaff. Meanwhile, Mr. Powell's top deputy met with top Pakistani officials in Washington.

A senior White House official says specific requests were made. The official indicates, among other things, Pakistan was asked to close its border with Afghanistan.

Pakistan has ties with the ruling Taleban movement in Afghanistan, which is sheltering Osama bin Laden. On Thursday, Secretary Powell identified the Saudi-born militant as a suspect in this week's terrorist attacks on the World Trade Center and the Pentagon.

The White House official, who spoke on condition of anonymity, said the Bush administration is waiting for a reply from the Pakistani government. The official said the White House is hopeful and has reason to believe Pakistan wants to help.

Earlier, President Bush was asked about President Musharaff's pledge to cooperate on combating terrorism. Mr. Bush said he appreciates the words, but he is waiting to find out if Pakistan is ready to act.