U.S. Defense Secretary Jim Mattis has arrived in Afghanistan on a previously unannounced visit to discuss the country’s security situation with political and military leaders.

Afghan Voice Agency(AVA), Mattis is expected to meet with U.S. General John Nicholson, the ground commander for international forces in Afghanistan, as well as Afghan President Ashraf Ghani and other top officials.

The visit comes days after about 10 Taliban militants killed at least 140 people in the deadliest insurgent raid on an Afghan military base in 16 years.

The militants were dressed as Afghan soldiers when they arrived at the regional headquarters of the Afghan National Army in Mazar-i-Sharif, the capital of Balkh province.

General Mohammad Radmanesh, a spokesperson of the Afghan Ministry of Defense, said that the militants were allowed on the base without all of the proper checks after pleading for urgent care for a man in their vehicle who was covered in blood.

The Taliban claimed responsibility for the attack and said it was in retaliation for the recent killings of Taliban shadow governors for Kunduz and Baghlan provinces.

The Afghan government is investigating the incident.

4-Year Security Plan

Mattis is visiting as Afghans are looking to President Ghani to announce a four-year security plan for the country in the coming weeks.

Afghan and U.S. officials say Mattis will be discussing the plan with Afghan leaders while in Kabul.

Possible elements of the four-year plan include the provision of up to 200 U.S. helicopters and other aircraft for Afghan forces, along with doubling the number of Afghan special forces, according to U.S. and Afghan officials familiar with the ongoing discussions.

However, a U.S. official stressed to VOA on Monday that the Pentagon is still working with Congress and the White House to firm up the new administration’s Afghanistan policy and financial commitments before making any final planning decisions.