Mike Mullen, the former chairman of the Joint Chiefs of Staff, said on Sunday that Russian President Vladimir Putin was a "cornered animal" after his military's stumbles in Ukraine.

During an interview on ABC's "This Week," the retired admiral said that he had a lot of options for an attack on Putin's nuclear weapons.

I think he's more and more dangerous because he's a cornered animal. We have to think through what the requirements are to respond to that. The need to get to the table is underscored by this.

According to Putin, his country's threat to engage in nuclear warfare was not a bluff.

Russia retreated from several parts of the country where they wanted to establish a foothold, as Ukrainian counteroffensives in the east blunted Moscow's long term plans for the country.

Thousands of Russian men left the country, unwilling to die in a conflict they did not support, despite Putin's recent declaration of a partial mobilize of reserve troops.

Petraeus said last week that the war looks very dire for Putin.

The bottom line is that the Ukrainians have done a better job of getting help from the United States and NATO than Russia has done.

The link between Russia and the Crimean Peninsula is "logistically critical" for Putin and could escalate the threats of an attack.