The latest talks between the Taliban and the US peace envoy on the war in Afghanistan focused on the withdrawal of Nato troops, the release of prisoners and halting attacks on civilians by pro-government forces, a Taliban spokesman said on Wednesday.

US envoy Zalmay Khalilzad, who tweeted that talks held this week in the United Arab Emirates were “productive,” was in Pakistan to meet with the chief of the country's army before heading to the Afghan capital Kabul later in the day. The UAE talks also involved Saudi, Pakistani and Emirati representatives.

The Taliban have refused to meet directly with the Afghan government, viewing it as a puppet of the US. The group controls nearly half of Afghanistan, and are more powerful than at any time since a 2001 US-led invasion. They carry out near-daily attacks, mainly targeting security forces and government officials.

In a significant development, three representatives of the Haqqani network Hafiz Yahya, Saadullah Hamas and Dr Faqeer, who goes only by a single name were also present at the talks, according to a Taliban official.

Editorial: US-Taliban talks

This would be the first time a US envoy has met with representatives of the Haqqani network, declared a terrorist group by Washington and considered one of the most lethal fighting forces in Afghanistan.

Although part of the Taliban, the Haqqani network has its own military committee. Its leader, Sirajuddin Haqqani, is deputy head of the Taliban. Their prowess on the battlefield makes their presence at the meeting particularly significant because it's unlikely any agreement could be enforced without their support.

At the meeting, Khalilzad pressed for the release of two professors from the American University of Afghanistan — American Kevin King, 61, and Australian Timothy Weeks — who were kidnapped from Kabul in August 2016, the Taliban official said. A 2017 video message from King revealed he was in poor health.

It is widely believed the two Westerners are being held by the Haqqani group. Haqqanis have been demanding the release of Anas Haqqani, a brother of Sirajuddin captured by Afghan intelligence agents in 2014. Apparently, Taliban leader Haibaitullah Akhundzada ordered the three to attend the UAE meetings, the official said.

“We called for an end to the invasion and they insisted on the exchange of prisoners, including teachers of the university,” said the Taliban official, adding there was no discussion about a cease-fire and “we do not hold any discussions on Afghanistan's internal issues with the Americans and we do not want any advice from anyone.”

Two former inmates at the US prison in Guantanamo Bay, ex-Taliban army chief Mohammed Fazle and former governor of western Herat province, Khairullah Khairkhwa, were also at the meetings.

The Afghan government sent a delegation that included the National Security Adviser Hamdullah Mohib to the UAE but it did not take part in the talks, instead holding separate talks with Khalilzad, who said he would meet with Afghan leaders later Wednesday in the Afghan capital.

Khalilzad's meeting with Pakistan's powerful army chief Gen. Qamar Javed Bajwa was presumably to brief him on the talks, which Pakistan helped orchestrate by getting the Taliban to the UAE. It seems likely Pakistan also played a part in getting the Haqqani network representatives to the meeting.

The U.S. Embassy in Pakistan said Khalilzad met with Bajwa to express “his appreciation for Pakistan's efforts to encourage the Taliban to negotiate directly with the Afghan government and other senior Afghan political figures to reach a political settlement that ends the war in Afghanistan.”

Taliban spokesman Zabihullah Mujahid said no direct talks with the Afghan government had yet been held. The Taliban view the Afghan government as an American puppet and have long demanded direct talks with the US.

Khalilzad said he would like to see a “roadmap” agreement reached before Afghan presidential elections, scheduled for next April.

Since being appointed in September, Khalilzad has met on several occasions with all sides to try to start direct peace negotiations between the Taliban and the Afghan government aimed at ending America's longest war, now in its 17th year.

Washington has spent nearly $1 trillion since 2001 when it led an invasion of Afghanistan to oust the Taliban after they harbored Osama bin Laden and his al-Qaida insurgent group, which carried out the 9/11 attacks against the US.