The United States warned Russia on Wednesday against military intervention in Ukraine and said any incursion could lead to a broad international backlash.

Secretary of State John F. Kerry also pledged $1 billion in emergency U.S. loan guarantees to help Ukraine’s new, temporary government as it reels from the ouster of President Viktor Yanukovych last weekend.

“I don’t think there should be any doubt whatsoever that any kind of military intervention that would violate the sovereign territorial integrity of Ukraine would be a huge — a grave — mistake,” Kerry said in a roundtable interview with reporters.

The United States, United Nations and others would react, Kerry said, without specifying how.

The Obama administration is trying to avoid a confrontation with Russia over the fate of the former Soviet republic, whose Russian-speaking eastern areas identify strongly with Moscow, while also firmly defending the former opposition figures now at the helm in Kiev.

Russian President Vladimir Putin on Wednesday ordered large-scale military exercises, raising fears that the decision was a prelude to invasion. The restive Crimean region on the Black Sea, once part of Russia proper, is seen as a potential flash point.

Kerry suggested it would be hypocritical for Russia to send in forces after objecting so forcefully to outside military action in Syria and Libya, but he also stressed that Washington is not looking for a fight.

“This is not ‘Rocky IV.’ It is not a zero-sum game,” Kerry told reporters. “We do not view it through the lens of East-West or Russia-the U.S. or anything else. We view it as an example of people within a sovereign nation who are expressing their desire to choose their future.”

The White House said President Obama and Putin had agreed on the importance of all sides refraining from violence in Ukraine when the two spoke by phone late last week. Kerry said he will see Russian Foreign Minister Sergei Lavrov next week.

Those who threw off the Yanukovych “kleptocracy” now badly need international help, Kerry said. He urged Ukraine to stick to a fast calendar for elections, while undertaking difficult fiscal reforms and anti-corruption measures that would allow wider investment by the International Monetary Fund.

The $1 billion U.S. loan guarantees would allow quick loans from the IMF or other international financial institutions. They would be followed by a much larger international aid package that is expected to include European and U.S. contributions and international loans.

“There’s got to be some reality here,” Kerry said. “I don’t think it’s enough for us to be heralding the advent of democracy and to applaud the courage and conviction of the people who brought about this transition and then just not do anything. I think that’s unconscionable.”

Ukraine’s deep fiscal crisis is one of the roots of three months of political upheaval that culminated in the abrupt ouster of Yanukovych. He had walked away from a European Union economic alliance last fall in favor of a short-term bailout from Moscow, setting off street protests and demands for his resignation.

Kerry also cautioned the former opposition not to overreach. The new government must answer to the people, or “they could then find themselves opposed by the very people who were pushing for these changes.”

Separately, Kerry predicted confidently that even if Afghan President Hamid Karzai continues to boycott a security agreement with the United States, his successor will agree to it. The agreement would allow a small number of U.S. troops to remain in Afghanistan after this year.

“It will be signed,” Kerry said.