U.S. Secretary of State Hillary Clinton arrived in Pakistan early Sunday as Washington struggles to change its relationship with “one of the most critical countries in the world,” according to a top U.S. official.

Clinton is on her way to Afghanistan, but the visit to Pakistan is just as important, said Richard Holbrooke, the special U.S. representative for Pakistan and Afghanistan.

The United States has an intense interest in what happens in the tribal regions on the Afghanistan-Pakistan border, Holbrooke said. Al Qaeda is thought to be based in the region.

The region is among Washington’s “highest priorities,” Holbrooke said, but to make progress, “we need to change the core of the relationship” between the United States, Pakistan and Afghanistan.

Clinton will announce a “massive” list of aid projects for Pakistan on Monday, according to a senior U.S. official who did not want to be named talking about the announcements before they are made.

“No country in the world is getting as much attention by the United States or more support because no country is more important,” the official said.

Clinton is expected to talk about U.S. plans to spend billions of dollars on social, economic and infrastructure development, especially in Pakistan’s tribal region. She is also likely to discuss U.S. plans to help with Pakistan’s energy and water shortage.

Clinton will travel next to an international conference in Kabul, Afghanistan, on Tuesday, and stop in South Korea and Vietnam before coming home.

During the Pakistan leg of her trip, she will meet with Prime Minister Yousuf Raza Gilani and President Asif Ali Zardari.

(Source: CNN)