WARSAW, May 24 (Reuters) - Polish President Andrzej Duda said on Wednesday he wants to hold a referendum in November 2018 on whether to change the country’s 20-year-old constitution, although it was not clear what kind of changes he was seeking.

Duda has said previously that the balance of powers in the current constitution, Poland’s first after the fall of communism, is incorrect.

He has avoided any specific changes he would like to see made to the document, although he has suggested that the president is commander-in-chief of the armed forces in name only.

“I will ask the Senate (Poland’s upper house of parliament) to hold a referendum on Nov. 11, 2018, in order to delineate the foundation of the future constitution,” Duda said on state-run television. Nov. 11 is Poland’s independence day.

The 45-year-old Duda, an ally of the conservative ruling Law and Justice (PiS) party, has said previously he would like Poles to decide whether there is a need for a new constitution.

The current constitution was adopted in April of 1997.

“In many cases, in my opinion, the division between powers was done incorrectly” in the 1997 constitution, Duda told Radio Dla Ciebie earlier this month.

He said that although the constitution stipulates that the president is the commander-in-chief of the armed forces, in practice it is very different.

“The president can propose, suggest different initiatives, but if the minister (of defence) does not agree, then the president in this case is trammelled. You can say it this way: the phrase ‘Commander-in-Chief’ is not reflected in practice.”

Nov. 11 next year will mark the 100th anniversary of the restoration of Polish sovereignty after 123 years of partition by the Russian Empire, the Kingdom of Prussia and the Habsburg Empire. (Reporting by Lidia Kelly; Editing by Hugh Lawson)