"We are looking to raise the horns and to address the world leaders to stop this aggression. It's the very first stage," Sergeyev said on CNN's "State of the Union."
"We are preparing to defend ourselves," he said. "Naturally, if aggravation is going in that way, when the Russian troops are enlarging with every coming hour, naturally we'll ask for military support and other kinds of support."
On Saturday, the Russian Parliament allowed President Vladimir Putin to deploy soldiers to Ukraine to help the autonomous Crimea region deter anti-government protesters. About 60 percent of people living in Crimea are ethnic Russians.
U.S. Secretary of State John Kerry said on CBS's "Face the Nation" Sunday this was "an incredible act of aggression" by Putin.
"You just don't in the 21st century behave in 19th century fashion by invading another country on completely trumped up pre-text," Kerry said. "It is serious in terms of sort of the modern manner with which nations are going to resolve problems. There are all kinds of other options still available to Russia. There still are. President Obama wants to emphasize to the Russians that there are a right set of choices that can still be made to address any concerns they have about Crimea, about their citizens, but you don't choose to invade a country in order to do that."
Meanwhile, Republican lawmakers in the United States have questioned whether Obama is being outmaneuvered by Putin.
"Putin is playing chess and I think we are playing marbles, and I don't think it's even close" House Intelligence Committee Chairman Mike Rogers, R-Mich., said on "Fox News Sunday." "They've been running circles around us. And I believe it's the naive position on the National Security Council and the president's advisers that, if we just keep giving things to Russia, they'll wake up and say, 'The United States is not that bad.' That is completely missing the motivations of why Russia does what Russia does."
Rep. Chris Van Hollen, D-Md., said Americans should be placing their doubt with Putin, not Obama.
"We're 48 hours from an international crisis, I would hope Americans would focus on condemning the actions of Putin rather than in a knee-jerk way, again, criticizing the president of the United States," Van Hollen said on "Fox News Sunday."
Sen. Dick Durbin, D-Ill., said on CNN's "State of the Union": "We've got to make it clear to Putin that if there are Russian speaking people on the soil of another nation, that doesn't give him license to invade -- to protect him when there's no obvious threat against him, because there are Russians spread all over the former Soviet empire there in countries that are today very free, very democratic, and very friendly to the United States. We've got to draw the line."