One tactic that has been used in modern American history to “punish” nations who are seen as a threat, as a danger, as an “outlaw” nation, is to suspend diplomatic relations with that nation, thinking that taking that action forces that country to change its policies, but it has never worked, and is a lost cause. It is more done to soothe the sensitivities of certain groups, and is a purely political act, with no real purpose and accomplishing nothing, except to isolate the people of those nations, who if anything, are harmed by American action, while the “outlaw” government goes on violating the human rights of their citizens.
Famous examples of nations we have refused to have relations with over a long period of years include:
Soviet Union, 1917-1933—16 years, ended by Franklin D. Roosevelt.
People’s Republic of China, 1949-1979—30 years, ended by Jimmy Carter, but beginning of ties and interaction under Richard Nixon in 1972 (23 years).
Cuba, 1961-Present—54 years, in the process of being ended by Barack Obama.
Iran, 1980-Present–35 years, possibly ending now under Barack Obama, with the potential nuclear agreement.
Diplomatic relations should NOT be about morals and ethics, as that does not work in international relations, but rather on practical reality, as nations we oppose are not going to collapse and disappear because we condemn their behavior. It is better to have some input into what goes on in those nations, unless, of course, the other nation involved chooses on its own to break off diplomatic relations.