The Pentagon says most U.S. troops on a mission to evacuate the Kabul embassy will arrive by Sunday and will be prepared to airlift thousands of people per day.

The first Marines have arrived at Kabul's international airport as part of a mission ordered a day earlier by President Joe Biden as the Taliban gains more territory amid the withdrawal of U.S. troops.

Pentagon spokesman, John Kirby, says "I expect that by the end of the weekend the bulk of the 3,000 (troops) will be in place... capacity is not going to be a problem," Kirby said of the airlifts, adding "we will be able to move thousands per day."

As of this week, some 4,200 people were working at the embassy in the Afghan capital and thousands of more Afghans who served as interpreters or in other support roles in the 20-year U.S. occupation are eager to escape for working with the U.S. military. 

Britain and several other Western nations are also sending troops amid fears the Taliban could take control of the capital Kabul. 

As U.S.-led foreign forces complete their withdrawal after 20 years of occupation, an Afghan government official confirmed that Kandahar, the economic hub of the south, was under Taliban control. The loss is a heavy blow to the government.

Diplomats say some embassies have begun to burn sensitive material ahead of evacuating. According to an advisory seen by media, the U.S. embassy in the Afghan capital informed staff that burn bins and an incinerator were available to destroy material including papers and electronic devices to "reduce the amount of sensitive material on the property"

Meanwhile, the United Nations Secretary-General, Antonio Guterres, warned that "Afghanistan is spinning out of control" and urged all parties to do more to protect civilians. "This is the moment to avoid a prolonged civil war" he said. 

Experts have slammed the 20-year American occupation of Afghanistan as nothing short of a complete disaster.