The message from Mullah Haibatullah Akhundzada, to mark the upcoming Eid al-Adha holiday, came a day after a Taliban suicide bomber killed 14 people and wounded 145 in Kabul in an attack the government said raised questions about the militants’ commitment to peace despite the talks with the United States.

Akhundzada called for trust but did not refer to Wednesday’s bombing in his message. He said the Taliban had taken “incredible strides” towards their goal of “ending the occupation and establishing an Islamic system”.

Addressing American officials, Akhundzada said the Taliban were engaged in negotiations with them with “utmost seriousness” and called for sincerity to end the “18-year tragedy”.

“However, the increasing blind and brutal bombings by America during the negotiation process, attacks on civilian areas and the contradictory statements by your military and political officials has generated a cloud of uncertainty about this process and raised doubts about your intentions,” he said.

“Bilateral trust is the foundation of a successful negotiations process therefore it is imperative that such negative actions are ceased,” Akhundzada said.

The negotiations, which began late last year in Qatar, have not brought a reduction in violence, with both the Taliban and Afghan government forces, assisted by U.S.-led international troops, launching assaults against each other.

At the same time, the violence has had virtually no impact on the talks. Both sides reported significant progress this week in their efforts to forge a deal.

The expected pact will be centered on a timeline for the withdrawal of U.S. troops in exchange for a Taliban promise that Afghanistan will not be used as a base for international terrorism, both sides have said.

About 20,000 foreign troops, most of them American, are in Afghanistan as part of a U.S.-led NATO mission to train, assist and advise Afghan forces. Some U.S. forces carry out counter-terrorism operations.

The Taliban said Wednesday’s bomb in Kabul was a response to daily attacks by government forces in the countryside.

Zalmay Khalizad, the U.S. envoy negotiating with the Taliban, condemned the Kabul blast and said the focus should be on reducing violence to prepare “intra-Afghan negotiations that will produce a political roadmap and a permanent ceasefire”.

A Taliban promise to talk peace with the U.S.-backed government is likely be part of any agreement with the United States, but many Afghan government officials fear their war with the Taliban will not end if and when the Americans leave.

The militants control more territory than at any point since the United States bombed them out of power in 2001.