* Taliban forces close in on biggest city in the north

* Speed of Taliban advance shocks government and allies

* Biden says he doesn’t regret decision to withdraw U.S. forces

The Taliban capture of Faizabad, capital of the northeastern province of Badakhshan, came as President Ashraf Ghani flew in to Mazar-i-Sharif to rally old warlords to the defence of the biggest city in the north as Taliban forces close in.

Jawad Mujadidi, a provincial council member from Badakhshan, said the Taliban had laid siege to Faizabad before launching an offensive on Tuesday.

“Unfortunately, after hours of heavy fighting the ANDSF retreated,” Mujadidi told Reuters, referring to national security forces. “With the fall of Faizabad the whole of the northeast has come under Taliban control.”

Badakhshan borders Tajikistan, Pakistan and China.

The loss of the city is the latest setback for the government, which has been struggling to stem the momentum of Taliban assaults in the last few months.

The Taliban are battling to defeat the U.S-backed government and reimpose strict Islamic law. The speed of their advance has shocked the government and its allies.

Taliban forces now control 65% of Afghanistan and have taken or threaten to take 11 provincial capitals, a senior EU official said on Tuesday.

U.S. President Joe Biden urged Afghan leaders to fight for their homeland, saying on Tuesday he did not regret his decision to withdraw, noting that the United States had spent more than $1 trillion over 20 years and lost thousands of troops.

The United States was providing significant air support, food, equipment and salaries to Afghan forces, he said.

The United States will complete the withdrawal of its forces this month in exchange for Taliban promises to prevent Afghanistan being used for international terrorism.

The Taliban promised not to attack foreign forces as they withdraw but did not agree to a ceasefire with the government. A commitment by the Taliban to talk peace with the government side has come to nothing as they eye military victory.

Some Afghans feel abandoned as the United States and other Western powers withdraw, leaving the Taliban to make their move.

“The U.S. did not provide support … now we see the result,” Dawlat Waziri, a retired general and military analyst, told Reuters.

REGIONAL APPEAL

The Taliban advances have raised fears of the return to power of the hardline militants who emerged in the early 1990s from the chaos of civil war and controlled most of the country from 1996 to 2001, when they were ousted by a U.S.-led campaign for harbouring al Qaeda chief Osama bin Laden.

A new generation of Afghans, who have come of age since 2001, fears that the progress made in areas such as women’s rights and media freedom will be squandered.

U.N. human rights chief Michelle Bachelet said on Tuesday reports of violations that could amount to war crimes and crimes against humanity were emerging, including “deeply disturbing reports” of the summary execution of surrendering government troops.

Afghan officials have appealed for pressure on Pakistan to stop Taliban reinforcements and supplies flowing over the border. Pakistan denies backing the Taliban.

The government has withdrawn its forces from some hard-to-defend rural districts to focus on holding population centres. In some places, government forces have given up without a fight.

During their 1996-2001 rule, the Taliban were never completely in control of the north but this time, they seem intent on securing it before closing in on the capital.

Ghani is now appealing for help from the old regional war lords he spent years sidelining as he attempted to project the authority of his central government over wayward provinces.

He was due to meet powerbrokers in Mazar-i-Sharif to work out coordination between the security forces and militias and operations to take back areas the Taliban captured, the president’s office said.

The city is largely cut off from the rest of the country by the Taliban who now also control electricity supplies from northern neighbours to Kabul.

In the south, government forces were battling Taliban fighters around the city of Kandahar and thousands of civilians from outlying areas had taken refuge there, a resident said.

Fighting was also taking place in city of Farah in the west, near the Iranian border, while the Ministry of Defence said in a statement security forces had also battled Taliban in Laghman, Logar, Paktia, Uruzgan, Zabul, Ghor, Balkh, Helmand, Kapisa and Baghlan provinces and 431 Taliban had been killed.

It gave no figure for casualties on the government side and a Taliban spokesman was not immediately available for comment.

The Taliban have captured districts bordering Tajikistan, Uzbekistan, Iran, Pakistan and China, heightening regional security concerns.

An EU official said on Tuesday they now controlled 65% of the country.

(Reporting by Kabul, Islamabad bureaus Editing by Robert Birsel and Nick Macfie)