DOHA, Qatar (Reuters) — Afghan government representatives and Taliban insurgents gathered on Saturday for historic peace talks aimed at ending two decades of war that has killed tens of thousands of combatants and civilians.

Ahead of face-to-face negotiations in coming days, the warring sides were urged by various countries and groups to reach an immediate ceasefire and forge an agreement that upholds women’s rights.

The government of U.S. President Donald Trump expressed its intention to use aid as leverage for a deal.

The opening ceremony came one day after the 19th anniversary of the 9/11 attacks on the United States that triggered its military involvement in Afghanistan.

Secretary of State Mike Pompeo urged the warring sides to seize the opportunity to strike a comprehensive peace deal, while acknowledging many challenges lay ahead.

“The choice of your political system is yours to make,” he told the opening ceremony in the Qatari capital Doha. “We believe firmly that protecting the rights of all Afghans is the best way for you to break the cycle of violence.”

The head of Afghanistan’s peace council, Abdullah Abdullah, said that even if the two sides could not agree on all points, they should compromise.

“My delegation are in Doha representing a political system that is supported by millions of men and women from a diversity of cultural, social and ethnic backgrounds in our homeland,” he said.

Taliban leader Mullah Baradar Akhund said that Afghanistan should “have an Islamic system in which all tribes and ethnicities of the country find themselves without any discrimination and live their lives in love and brotherhood.”

Pompeo warned that the size and scope of future U.S. financial assistance to the country, which relies heavily on international funding, would depend on their “choices and conduct.” U.S. Special Envoy Zalmay Khalilzad told reporters that preventing terrorism was the chief condition but that protecting minority and women’s rights would also influence any future decisions on Congress-allocated funding. “There is no blank check.”

Officials, diplomats and analysts say that although getting both sides to the negotiating table was a major achievement, this does not mean the path to peace will be easy, especially with violence increasing around the country.

The two sides sat down after the opening ceremony to discuss how the talks will proceed, officials said.

How to include the Taliban, who have rejected the legitimacy of the Western-backed Afghan government, in any governing arrangement and how to safeguard the rights of women and minorities who suffered under Taliban rule are also big challenges.

“The Afghan people must be at the heart of this peace process…that leaves no one behind, including women,” said Indonesian Foreign Minister Retno Marsudi.

Pompeo noted the four women negotiators among the Afghan delegation, saying they exemplified the gains in Afghanistan of female participation in public life. He urged that the country’s social advances be protected.

Watching on television in the Afghan capital Kabul, teacher Pariwash Farkish said that although she had witnessed violent blasts and peace talks were very important to her, she harboured concerns.

“While I was watching the ceremony today, I saw there were no woman among the Taliban, and that worried me,” she said.

Then-president George W. Bush sent U.S. forces into Afghanistan a month after the 9/11 attacks to hunt down their mastermind, Osama bin Laden, a Saudi given sanctuary by the country’s Islamist Taliban rulers.

Although the Taliban regime was quickly toppled, they regrouped and have since waged an insurgency that has sucked in Afghanistan’s neighbors and troops from dozens of countries, including NATO forces.

Negotiations to broker a comprehensive peace deal were a component of a troop withdrawal pact signed between the United States and the Taliban in February. After months of delay, a dispute over the Taliban’s demand for the release of 5,000 prisoners was resolved this week.

Ahead of the U.S. presidential election in November, Trump is looking to show progress on his pledge to end America’s involvement and pull out most of the foreign forces stationed in Afghanistan.