The first of a total of 30,000 extra U.S. soldiers to be deployed to Afghanistan will arrive in the country this week, the head of the U.S. Joint Chiefs of Staff said Monday.

"I told our troops heading here to steel themselves for more combat and more casualties," Adm. Mike Mullen, who is in Afghanistan on a visit, said.

He also said that "the insurgency has grown more violent, more pervasive, more sophisticated."

Mullen also welcomed NATO's decision to send 7,000 additional troops to Afghanistan.

In early December, U.S. President Barack Obama said in a televised address to the nation that the United States would send an additional 30,000 troops to Afghanistan in the first part of 2010 to defeat the Taliban and establish law and order. However, the president said, the U.S. would start withdrawing its troops in 18 months.

The NATO-led International Security Assistance Force (ISAF) and a separate U.S.-led coalition, involved in Operation Enduring Freedom, have a total of 112,000 troops in Afghanistan. The U.S. has by far the largest force, with some 68,000 troops.

KABUL, December 14 (RIA Novosti)