An idea. Tell them:

For personal reasons I would like to delay the training until xx. If that is not an option I can attend. I prefer to delay if it is convenient for you.

If they say I need to attend now and you later quit you can tell them that was the personal reason for wanting to delay.

Even if you don't get fired you will go to the bottom of the list for training, long project, and promotion. You are announcing you don't intend to stay.

An idea. Tell them:

For personal reasons I would like to delay the training until xx. If that is not an option I can attend. I prefer to delay if it is convenient for you.

If they reply you need to attend now and you later quit you can tell them that was the personal reason for wanting to delay.