WASHINGTON - The failure of the United States and its allies' 20-year costly war in Afghanistan further proves that military intervention is no solution to some international and regional conflicts, a famous US professor has said.

"The United States and its allies have been in Afghanistan for 20 years, spending trillions of dollars. Now they are pulling out of Kabul in a hurry. Unfortunately, there has been no major change in the livelihood of Afghans and the situation in the war-torn country has become more fragile and uncertain," Zhu Zhiqun, professor of International Relations and Political Science at Bucknell University, told Xinhua in an interview.

"What is unfolding in Afghanistan shows that some international and regional conflicts cannot be resolved through unilateral military intervention or war" but rather through "peaceful negotiations and consultation," said Zhu, describing the chaotic withdrawal from Kabul as a blow to the image of the United States and its military.

"Regional countries and international institutions have to help ensure Afghanistan maintain stability and avoid becoming a breeding ground for extremism and terrorism," Zhu urged.

The expert hoped that all countries would cut their arms expenditure and focus more on their economy, social development as well as education for the young people.

"The international community must make every effort to help countries like Afghanistan in this regard because the root cause of extremism and terrorism is poverty and lack of education," Zhu explained.

"Military means cannot eradicate extreme ideology and terrorism. This is what proved true in Afghanistan," he said.