Equivalent to the Chinese quote, (mis)attributed to JFK: "We fear not God-like rivals, but pig-like team members"

I've been looking for an English equivalent of the Chinese, "不怕神一样的对手 就怕猪一样的队友," which has been, rather directly, translated as:

We fear not God-like rivals, but pig-like team members

and rather funnily enough attributed to JFK.

• Did JFK ever say anything even remotely close to this?

• Are there other idiomatic phrases in English that resemble "We fear not God-like rivals, but pig-like team members"? (i.e: who needs enemies, with friends like you?)

(With apologies and thanks to Janus)

Keep your enemies close, but your friends closer.

It's sometimes used as an ironic twist on

Keep your friends close, but your enemies closer.

This is a quote, but it reads like a proverb.

A strong foe is better than a weak friend. (Edward Dahlberg)

I have also found other expressions of your version:

A weak teammate does more harm than the enemy.

and

What one should really fear is not a competent enemy, but an incompetent ally.

[Aside: I can't resist posting this quotation from Oscar Wilde which I found while doing research for this answer:

Always forgive your enemies - nothing annoys them so much.]