“Why should we be closer to the Soviets? Because the Americans have challenged us. America is involved in a conspiracy [against the Arab world], primarily because of its policy toward Israel. In our view, whoever is against the Americans stands with us. The enemy of your enemy is your friend.”

There Will Be No Reconciliation with America before Withdrawal, Apology, and Compensation http://www.memritv.org/Transcript.asp?P1=1402, exclusive interview, March 2007.
Targeting collaborators

2000s, 2003, Mission Accomplished (May 2003)

Source: The Goblin Quest Series, Goblin Hero (2007), Chapter 7 (p. 117)

Machiavelli commented on the relative ease of gaining favor from friends and enemies in Chapter 20 of The Prince, quoted above. However, this particular wording comes from a line spoken by Michael Corleone in The Godfather Part II (1974), written by Mario Puzo and Francis Ford Coppola:
My father taught me many things here. He taught me in this room. He taught me: keep your friends close, but your enemies closer.
Misattributed

This has often been attributed to Sun Tzu and sometimes to Petrarch. It comes most directly from a line spoken by Michael Corleone in The Godfather Part II (1974), written by Mario Puzo and Francis Ford Coppola:
My father taught me many things here. He taught me in this room. He taught me: keep your friends close but your enemies closer.
Niccolò Machiavelli, who is also sometimes credited, wrote on the subject in The Prince:
It is easier for the prince to make friends of those men who were contented under the former government, and are therefore his enemies, than of those who, being discontented with it, were favourable to him and encouraged him to seize it.
Misattributed

"The Poodle Gets Kicked" http://buchanan.org/blog/the-poodle-gets-kicked-3731 (March 15, 2010), Patrick J. Buchanan
2010s

2000s, 2009, The Left's love affair with Islam (2009)

2000s, 2004, Speech at the Republican National Convention (2004)