Frans van Anraat, 62, is charged with supplying thousands of tonnes of raw materials for chemical weapons used in the 1980-1988 war against Iran and against Iraqi Kurds, including a 1988 battle over the town of Halabja, in which an estimated 5000 people were killed.
Prosecutors say the United Nations has described Van Anraat, who is also charged with complicity in war crimes and genocide, as "one of the most important middlemen in Iraq's acquisition of chemical material".
Prosecutors and the defence are expected to discuss preparations for trial at Friday's hearing at a high-security court in the port city of Rotterdam.
"The images of the gas attack on the Kurdish city Halabja were a shock. But I did not give the order to do that. How many products, such as bullets, do we make in the Netherlands?" Van Anraat said in a 2003 interview with Dutch magazine Revu.
Van Anraat was arrested by Dutch officials at his Amsterdam home in December.
He was also detained in Milan in January 1989 following a US request but was released after two months. He then went to Iraq where it is thought he stayed until the 2003 US-led invasion, when he returned to the Netherlands through Syria.
The United States said Iraq's suspected weapons of mass destruction were one of its main reasons for going to war in 2003, but it has yet to find significant stockpiles.