U.S. Defense Secretary Robert Gates once again repeated Washington's resolve on Thursday to defeat the Taliban and al-Qaida network in Afghanistan and in the region.

U.S. Secretary of Defense Robert Gates attends a press conference with Afghan President Hamid Karzai (unseen) after their meeting in Kabul, Afghanistan, Sept. 2, 2010. Gates arrived in Kabul on Thursday for an unannounced visit. [Wang Yan/Xinhua]

"Taliban should know that we would continue to fight against them and the objective of the Untied States is to defeat Taliban and al-Qaida in Afghanistan and in the region," Gates told reporters at a joint press conference with Afghan President Hamid Karzai in Kabul.

He also said that the United States would continue to work with Pakistan to check militants' activities on its soil.

The Pentagon chief made these remarks amid an increase in Taliban activities and soaring casualties for NATO-led forces in Afghanistan.

More than 490 NATO soldiers, most of them Americans, have been killed in Taliban-linked activities in Afghanistan since the beginning of this year.

For the whole year of 2009, according to media reports, 521 NATO soldiers were killed.

Gates' unannounced visit to Afghanistan coincided with the killing of 10 civilians by NATO-led troops in the militancy-hit country.

However, he promised that NATO-led forces would do their best to avoid harming civilians.

The visiting U.S. defense secretary also said that the scheduled beginning of troops withdrawal in July 2011 does not mean abandoning Afghanistan, and that the United States would continue with its economic, military and political support to the country.

For his part, President Karzai said that in his talks with Gates, matters of mutual interests, including the situation in Afghanistan and war on terror, came under discussion.

The Afghan leader stressed that strained relations between Afghanistan and the U.S. would serve neither sides.

He said that he urged a change of strategy in the war on terror and Gates expressed his consent.

The relations between Afghanistan and the U.S. have recently turned tense over alleged corruption in the Afghan administration and the White House's pressure on Kabul to fight it.