NEW YORK- The U.N. special envoy on Afghanistan warned on Tuesday that Taliban insurgents have taken more than 50 of 370 districts in the country since May and that increased conflict "means increased insecurity for many other countries, near and far".

"Those districts that have been taken surround provincial capitals, suggesting that the Taliban are positioning themselves to try and take these capitals once foreign forces are fully withdrawn," Deborah Lyons told the U.N. Security Council.

After 20 years, the United States has started a withdrawal of its remaining 2,500 troops in Afghanistan and aims to be completely out of the country by Sept. 11. Around 7,000 non-U.S. forces from mainly NATO countries - along with Australia, New Zealand and Georgia - are also planning to leave by Sept. 11.

Lyons said the announcement earlier this year that foreign troops would withdraw sent a "seismic tremor" through Afghanistan, and that while this was expected, "its speed - with the majority of troops now already withdrawn - was not.

"All of the major trends - politics, security, the peace process, the economy, the humanitarian emergency, and of course COVID - all of these trends are negative or stagnate," Lyons told the 15-member Security Council. "The possible slide toward dire scenarios is undeniable."

U.S.-backed Afghan forces toppled the radical Islamist Taliban from power in late 2001 for refusing to hand over al Qaeda leader Osama bin Laden after the Sept. 11, 2001, attacks on the United States.

U.S. President Joe Biden will meet at the White House with Afghan President Ashraf Ghani and the chairman of Afghanistan's High Council for National Reconciliation, Abdullah Abdullah, on Friday amid the surge in fighting. 

Talks in Qatar between the Taliban and Afghan government representatives on a political settlement have stalled.

"There is only one acceptable direction for Afghanistan ... away from the battlefield, and back to the negotiating table," Lyons said. "The United Nations Security Council, with the support of the regional countries, must do all it can to push the parties in that direction."

(Reporting by Michelle Nichols; Editing by Andrew Heavens and Mark Heinrich) ((michelle.nichols@tr.com; Twitter: @michellenichols))