(Refiles to add UPDATE 1 to the headline)
(Updates with details, background, share price)
TORONTO, Jan 20 (Reuters) - Belinda Stronach, who is expected to announce her candidacy for the leadership of the Canada's Conservative Party later in the day, resigned on Tuesday as president and chief executive of auto-parts maker Magna International .
Her father, Magna founder and chairman Frank Stronach, will become interim president until the company, the world's seventh-largest auto-parts manufacturer, finds a permanent replacement. Belinda Stronach's resignation is effective immediately, Magna said in a statement.
Stronach, 37, will hold a press conference on Tuesday morning, at which she is expected to announce she is joining the Conservative Party's leadership contest.
She will be the third candidate to throw their hat into the ring alongside Stephen Harper, who stepped down as Alliance Party leader to run, and former Ontario health minister Tony Clement.
Party members choose a new leader in March.
The Conservative Party was reborn early last month when Canada's two right-wing opposition parties -- the Canadian Alliance and the Progressive Conservatives -- merged to challenge the ruling Liberals, who have been in power for a decade. A federal election is likely this spring.
Analysts have said Stronach's departure is unlikely to significantly disrupt Magna because of its decentralized management structure.
Magna's class A shares were down 83 Canadian cents at C$106.17 on Tuesday morning in light volume on the Toronto Stock Exchange.
($1=$1.29 Canadian)