JAKARTA (Reuters) - Indonesia's presidential frontrunner Joko "Jokowi" Widodo will on Monday announce popular former vice president Jusuf Kalla as his running mate for the July 9 election, party officials said.

A coalition of four parties led by Jokowi's Indonesian Democratic Party-Struggle gathered in central Jakarta to formally nominate Kalla, long a favorite for the position, according to opinion polls.

"(Kalla) has been invited...to become a vice presidential candidate," Max Lumintang of Golkar party told Reuters. "It's final, since last night."

Kalla is a member of the country's second biggest party Golkar and brings with him a significant support base.

Jakarta stocks rose more than 1 percent to an almost 1-year high in early trading on expectations that Jokowi would pick Kalla, a successful businessman and currently the head of Indonesian Red Cross.

(Reporting by Fergus Jensen, Writing by Kanupriya Kapoor, Editing by Jonathan Thatcher)