The U.S. and the Taliban are set to sign a historic agreement designed to pave the way to ending America's longest war, the bitter foes announced Friday, hours after Kabul said a weeklong partial truce across Afghanistan would kick off this weekend.

If that so-called "reduction in violence" holds, it would mark a major turning point in the grueling conflict and set the conditions for a deal that could, ultimately, result in U.S. troops pulling out after more than 18 years and launch Afghanistan into an uncertain future.

Both U.S. Secretary of State Mike Pompeo and the Taliban issued statements saying they'd agreed to sign the accord on February 29 in Doha, the capital of Qatar, following the one-week partial truce.

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"Upon a successful implementation of this understanding, signing of the U.S.-Taliban agreement is expected to move forward," Pompeo said, adding negotiations between the Taliban and the Afghan government would "start soon thereafter."

He also tweeted about the latest developments:

After decades of conflict, we have come to an understanding with the Taliban on a significant reduction in violence across #Afghanistan. This is an important step on a long road to peace, and I call on all Afghans to seize this opportunity. — Secretary Pompeo (@SecPompeo) February 21, 2020

Afghan National Security Council spokesman Javed Faisal and Taliban sources of Agence France Press said earlier that the "reduction in violence" between US, Taliban and Afghan security forces would begin Saturday.

The Associated Press quotes a senior U.S. State Department source as saying the seven-day "reduction of violence" will start Friday night.

Washington has been in talks with the Taliban for more than a year to secure a deal in which it would pull out thousands of troops in return for Taliban security guarantees and a promise to hold peace talks with the government in Kabul.

The weeklong reduction in violence would show the Taliban can control their forces and demonstrate good faith ahead of any signing, which would likely see the Pentagon withdrawing about half of the 12,000-13,000 U.S. troops currently in Afghanistan.

In a statement, the Taliban said warring parties would "create a suitable security situation" ahead of a deal signing.

One Taliban source in Pakistan told AFP that if an agreement is signed on February 29, talks between the Taliban and the Afghan government needed to cement a broader peace deal are slated to start March 10.

Russia on Friday hailed the accord between the United States and the Taliban as an "important event" for peace in Afghanistan.

And NATO chief Jens Stoltenberg on Friday welcomed the pact, saying it had opened a possible route to sustainable peace in Afghanistan.

In Afghanistan's southern province of Kandahar, which is seen as the Taliban's heartland, one insurgent told AFP he had received orders to stand down.

However, another Taliban commander based in Kandahar, Hafiz Saeed Hedayat, said he'd only been ordered to refrain from attacking major cities and highways. "This means maybe the violence will continue in the districts," Hedayat said.

Taliban expert Rahimullah Yusufzai said the move signaled a wider change in thinking for both the Taliban and the US after years of fighting.

"Both sides have shown their commitment to sign the peace deal, and it's a big development -- a significant one," he said.

The U.S. and the Taliban have been tantalizingly close to a deal before, only to see President Trump nix it at the eleventh hour in September amid continued insurgent violence.

Any truce comes fraught with danger, and analysts warn the attempt to stem Afghanistan's bloodshed is laced with complications and could fail at any time.

Worse still, they say warring parties could exploit a lull to reconfigure their forces and secure a battlefield advantage.

The reduction in violence is "still just the first step to get to intra-Afghan negotiations," Andrew Watkins, a senior analyst with the International Crisis Group, told AFP. "Those talks will be a tough road of their own, but are the best avenue to peaceful settlement to Afghanistan's conflict."