U.S. Defense Secretary Chuck Hagel arrived in Islamabad Monday.
He will meet with Prime Minister Nawaz Sharif in the first visit to Pakistan by the top Pentagon official in several years.
Secretary Hagel is expected to discuss Afghanistan, security threats and the blockage of a NATO supply route to Afghanistan spearheaded by a political party as a protest against U.S. drone strikes against suspected militants in Pakistan.
Hagel had been in Afghanistan since Saturday where Defense Minister Bismillah Khan Mohammad assured him a security pact with the United States will be signed in a "timely manner" despite Afghan President Hamid Karzai's reluctance.
Afghanistan's grand assembly, or Loya Jirga, has urged Mr. Karzai to sign the pact.
Mr. Karzai has refused to sign the security pact, which calls for some U.S. troops to stay in Afghanistan after 2014 to help train Afghan forces in their fight against the Taliban.
Mr. Karzai has said he wants his successor to decide on the security agreement after his country's presidential election in April.
The U.S. has said Mr. Karzai must sign the pact by the end of this year, or the U.S. will have no choice but to withdraw all troops after 2014.