A decision to prosecute Avigdor Lieberman would shake up Israeli politics since he has said he will resign if indicted, and his departure could mean a steep drop in support for his hard-line party, built largely on his personal popularity.

Lieberman's party, Yisrael Beitenu, is the key coalition partner in Prime Minister Benjamin Netanyahu's government.

An assistant to Israel's attorney general sent a letter to the good-governance group Ometz on Thursday saying a decision would be made by the end of next month, according to reports in the dailies Haaretz, Maariv and elsewhere.

The decision follows a decade-old investigation into Lieberman's business dealings, involving suspicions of bribery, breach of trust and other allegations. In 2009, upon completing the investigation, police said there was enough evidence to indict and turned the case over to the attorney general.

Lieberman says he is innocent and that the charges are politically motivated.

A blunt-talking Moldova-born politician, Lieberman has amassed power with support from immigrants from the former Soviet Union and with rhetoric attacking Israeli Arabs and dovish groups.