US Defence Secretary Roberts Gates arrived in Kabul on Saturday, making his farewell trip to Afghanistan after leading the Afghan war for nearly five years, officials said, reported dpa.
The Pentagon chief was expected to visit representatives of the around 100,000 US troops in the country and meet Afghan President Hamid Karzai, a presidential palace official said.
Gates and Karzai are expected to address a joint press conference later on Saturday, the spokesman said.
Gates, who is retiring at the end of the month, was visiting the war-torn country as the US was set to begin drawing down its troops in the country. President Barack Obama said last year the process would begin in July.
During his 12th trip to Afghanistan, Gates warned against rhetoric heard in Washington calling for a reduction in US military spending over coming years.
"The success of the mission should override everything else," he said.
"The most costly thing of all would be to fail," Gates warned, according to New York Times.
Given budget problems in Washington, some US legislators have said that the cost of Afghan war - more than 100 billion dollars a year - is unacceptable.
They point to the death of al-Qaeda leader Osama bin Laden, the initial target of US troops almost 10 years ago.
Gates is also expected to discuss with Karzai how to minimize civilian casualties from US-led operations against insurgents.
Earlier this week, Karzai condemned the killing of civilians by foreign forces in the strongest-ever term, warning the international forces of severe retaliation by the Afghan people if deaths continued to occur.