With the last U.S. forces on the way out of Afghanistan, U.S. President Joe Biden assured Afghan President Ashraf Ghani of U.S. diplomatic and humanitarian support on Friday as Taliban advances piled pressure on the U.S.-backed government in Kabul.

In a phone call, Biden and Ghani "agreed that the Taliban's current offensive is in direct contradiction to the movement's claim to support a negotiated settlement of the conflict," a White House statement said.

Biden has set a formal end to the U.S. military mission in Afghanistan for August 31, as he looks to disengage from a conflict that started after al-Qaeda attacked the United States on September 11, 2001.

Violence has risen sharply since the withdrawal plan was announced in April, with the Taliban launching offensives, taking districts and important border crossings, and encircling or closing in on several provincial capitals.

The Taliban control about half of Afghanistan's district centers, the senior U.S. general said this week, indicating a rapidly deteriorating security situation.

Biden told Ghani the United States would remain engaged diplomatically "in support of a durable and just political settlement," the White House said.

The United States is also preparing to begin evacuating thousands of Afghan applicants for special immigration visas (SIVs) who risk retaliation from Taliban insurgents because they worked for the U.S. government.

Biden on Friday authorized up to $100 million from an emergency fund to meet "unexpected urgent" refugee needs stemming from the situation, the White House said.

Biden also authorized the release of $200 million in services and articles from the inventories of U.S. government agencies to meet the same needs, it said.

The State Department condemned the Taliban's targeted attacks on former interpreters and other Afghans, as well as the destruction of infrastructure.

"We vehemently condemn the targeted attacks, the destruction of vital infrastructure, as well as other attacks against the people of Afghanistan," spokeswoman Jalina Porter said at a regular news briefing.