WASHINGTON (Reuters) - The warned on Tuesday that Washington and its allies would stand united in their defense of and that NATO territory was inviolable and the alliance would defend every single piece of it.

"Today seeks to change the security landscape of Eastern and ," Kerry said in a speech in Washington referring to 's occupation of Crimea and the threat it posed to .

"Whatever path chooses, the and our allies will stand together in our defense of ," Kerry said.

"And most important, together we have to make it absolutely clear to the Kremlin that NATO territory is inviolable. We will defend every single piece of it," he added.

In a call to NATO members, Kerry said unity was vital and members' defense budgets could not be allowed to shrink.

"Together we have to push back against those who want to change sovereign borders by force," Kerry said.

"We find ourselves in a defining moment for our trans-Atlantic alliance; Our strength will come from our unity," he said. "This moment is about more than just ourselves - the fact is that our entire model for global leadership is at stake."

Kerry said the and its European allies had to work together to ensure European countries were not dependent on Russian energy supplies.

"We can deliver greater energy independence if we help to diversify the energy sources available to European markets," he said in the address at a Washington think tank attended by ministers from several EU and NATO countries.

He called the crisis in "a wakeup call" to accelerate work "to promote a stronger, more prosperous trans-Atlantic community."