WASHINGTON  The Obama administration is stepping up pressure on Pakistan to expand and reorient its fight against the Taliban and Al Qaeda, warning that failing to do so would undercut the new strategy and troop increase for Afghanistan that President Obama is preparing to approve, American officials say.

While Afghanistan has dominated the public discussion of Mr. Obama’s strategy, which officials say could be announced as early as this week, Pakistan is returning to center stage in administration planning. As the president traveled to Asia, his national security adviser, Gen. James L. Jones, was quietly sent to Islamabad, its capital.

His message, officials said, was that the new American strategy would work only if Pakistan broadened its fight beyond the militants attacking its cities and security forces and went after the groups that use havens in Pakistan for plotting and carrying out attacks against American troops in Afghanistan, as well as support networks for Al Qaeda.

General Jones praised the Pakistani operation in South Waziristan but urged Pakistani officials to combat extremists who fled to North Waziristan.