The militant group has been repeatedly accused of conducting attacks against aid workers and infrastructure projects
The militant group, which has been repeatedly accused of conducting attacks against aid workers and infrastructure projects, made the surprise gesture in a statement.
"The Islamic Emirate (Taliban) not only backs all national projects which are in the interest of the people and result in the development and prosperity of the nation but are also committed to safeguarding them," the statement said.
"The Islamic Emirate directs all its Mujahideen to help in the security of all national projects that are in the higher interest of Islam and the country."
The statement comes after Afghan and Turkmen leaders on Monday inaugurated a railway line connecting Afghanistan to Europe through Turkmenistan.
According to the statement, the promise extends to highways, railways, as well as the $10 billion Turkmenistan-Afghanistan-Pakistan-India (TAPI) gas pipeline project, and a multi-billion dollar copper mine known as Mes Aynak, south of the Afghan capital Kabul.
Afghan officials were sceptical of the promises.
"They inflicted more than two billion dollars worth of damage to public and private properties and infrastructure during two months of their violent campaign in Afghanistan," Shahhussain Murtazawi, a spokesman for Afghan president Ashraf Ghani, told AFP, referring to the Taliban's fall offensive this year.
"How could we trust them now? They have to prove their promises in action," he added.
Decades of war have destroyed much of Afghanistan's basic infrastructure and fostered a climate of insecurity that has put investors to flight and forced millions of Afghans to become refugees.
The new Afghan government, which came to power in 2014, pledged an ambitious series of reforms to revive the economy and attract investment, although the ongoing insecurity and violence remain a serious challenge.