Cannot get NSTimer working in another thread

I need to create timers in another thread (not on main):

@implementation AppDelegate {
    NSThread* _worker;
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    _worker = [[NSThread alloc] initWithTarget:self selector:@selector(main) object:nil];
    [_worker start];
}

- (void)main {
    [NSTimer scheduledTimerWithTimeInterval:1
                                      target:self
                                    selector:@selector(timer_tick:)
                                    userInfo:nil
                                     repeats:YES];

    [NSThread sleepForTimeInterval:INFINITY];
    NSLog(@"**********************");
}

- (void)timer_tick:(NSTimer*)timer {
    NSLog(@"%@", NSThread.currentThread);
}

The timer never gets fired. What's wrong with my code?