U.S. President Barack Obama chose his words carefully when asked whether Russia’s recent actions in Ukraine should be considered an invasion, an indication of how the White House continues to judiciously avoid the use of that particular word fearing its geo-political ramifications.

"I consider the actions that we’ve seen in the last week a continuation of what’s been taking place for months now," Obama told reporters.

Minutes before, the president had referred to the situation as "this ongoing Russian incursion" into Ukraine that will "only bring more costs and consequences for Russia."

'Discussion of terminology'

In an interview on Thursday with MSNBC's Andrea Mitchell, State Department official Jen Psaki was pressed on the point: "If there's artillery firing across the border and tanks moving and movements of soldiers, what's the difference between an incursion and an invasion?"

"I think this is a discussion about terminology" Psaki responded, adding that "what we've seen here is an escalation of aggression by the Russians, a pattern, actually, over the last several months."

Psaki was also pressed on the issue by reporters asking why the White House refused to use the term and that Ukraine itself was calling it an invasion.

However, the State Department official remained on message: "I think our focus is more on what Russia is doing, what we’re going to do about it than what we’re calling it," Psaki said.

Pro-Russian rebels have opened a new front and pushed Ukrainian troops out of a key town in strategic coastal territory along the Sea of Azov. Kyiv and Western countries say the reversal was the result of the arrival of armoured columns of Russian troops, sent by Moscow to prop up a rebellion that would otherwise have been near collapse. (Mstislav Chernov/Associated Press) The diplomatic tiptoeing around the word comes as pro-Russian rebels suddenly opened a new front and pushed Ukrainian troops out of a key town in strategic coastal territory along the Sea of Azov. Kyiv and Western countries say the reversal was the result of the arrival of armoured columns of Russian troops, sent by Putin to prop up a rebellion that would otherwise have been near collapse.

Other Western leaders have also avoided use of the "invasion" word, except Canada, which continues to employ tough rhetoric against Moscow.

But for the U.S. and other Western countries, careful language is not surprising, particularly with politically loaded words like invasion, which can spark historical comparisons to Hitler's invasion of Poland or Saddam's invasion of Kuwait.

Obligated to find a cure

"The more you hype it, the more you diagnose the severity of the illness, the more you're obligated, either morally, politically or practically, to find a cure," said Aaron David Miller, a foreign policy expert and scholar at the Woodrow Wilson International Centre for Scholars

"And there's a certain reality here. There's a tendency on the part of this administration to allow its rhetoric to exceed its capacity to deliver," Miller said "We're not going to be able blunt or stop Putin's objectives in eastern Ukraine any more than we could stop the aggrandizement of Crimea."

Elliott Abrams, a senior fellow at the Council on Foreign Relations, said officials avoid using the word for the same reason the U.S. wouldn't call Egypt's military ouster of former president Mohammed Morsi a coup or why some mass slaughters aren't referred to as genocide.

U.S. President Barack Obama has ruled out military intervention in the ongoing Ukraine crisis. (Charles Dharapak/Associated Press)

"Some words have both legal and emotional effects. And in the case of invasion, it's emotional and political," Abrams said.

"I think they don't want to use the word invasion because it makes harder the next question: And what are you going to do about it?"

Obama and his Western allies have so far ruled out any kind of military intervention in the ongoing crisis, instead seeking to increase economic sanctions to punish Russia. Calling the crisis an invasion would raise expectations that a response to that invasion will be be robust "when the chances are that the Western response will be anything but robust," said Randall Hansen, director of the University of Toronto's Centre for European, Russian and Eurasian Studies.

Meanwhile,Canada isn't subject to the same expectations of military action, allowing its officials to be more bold, Hansen said.

"It's partly the freedom of not mattering," said Hansen. "The Canadian government can shout and scream as much as it likes knowing that it doesn't really have to do anything. In contrast, Obama and [German Chancellor Angela] Merkel have to measure every word because the entire world is hanging on them and have a level of responsibility that neither Harper or Baird has or will have."