Ahead of Crimea referendum, US senators in Kiev, anti-gov protests in Moscow

March 10, 2014: A woman with a Russian flag that reads "Crimea" amid demonstrators for Russians in Crimea, Moscow, Russia. (AP)

With a referendum just hours away in the Ukraine region of Crimea on whether to break away from Ukraine and join Russia, both sides on Saturday turned up the rhetoric, including U.S. leaders and the tens of thousands who protested in Moscow against the Kremlin-backed initiative.

"Say no to war" and "Putin, go away" shouted protestors, angry that President Vladimir Putin sent troops into Crimea amid Ukraine’s recent political upheaval, in an apparent attempt to annex the neighboring region.

It was the largest anti-government demonstration since 2012 and it took place near a rally of several thousand in support of Russian intervention in Crimea.

Crimea's referendum Sunday has been loudly condemned as illegitimate by much of the international community. As heavily armed forces apparently under Russian command have effectively taken control of the peninsula, the vote to join Russia has been widely criticized as a mere formality.

The vote is scheduled to take place from 2 p.m. to 4 p.m. Washington time. Officials will have 10 days to count the votes. However, such votes are usually counted within 24 hours. The two referendum questions before Crimean residents are: Do you support joining the Russian Federation? And, Do you support reenactment of 1992 Crimean constitution and Crimean status as a part of Ukraine?

“Ukraine has been invaded,” Arizona GOP Sen. John McCain said Saturday from Kiev. “Free peoples and patriots wish to defend themselves and their homes from aggression. I believe we should provide it.”

He was part of a U.S. delegation that included Indiana Sen. Dick Durbin, the Senate’s No. 2 Democrat, who said Americans are among the “millions across the world” who support Ukraine in its effort to hold a vote to achieve a government of the people.

The U.S. and Kiev have already said they will not recognize the results of the referendum.

U.S. Secretary of State John Kerry said the U.S. won't recognize the results of the referendum and warned "there will be some sanctions" if it goes forward. Further, he said, "there will be consequences if Russia does not find a way to change course."

Kerry also referred to the referendum as "illegal" following a five hour meeting with Russian Foreign Minister Sergei Lavrov in London Friday, which was described as an attempt to "de-escalate" the stand-off.

On Saturday, Russia vetoed a U.N. Security Council declaring the referendum invalid.

As we have made clear … we see Cold War dichotomy,” U.S. Ambassador to the United Nations Samantha Power said Saturday. “The United States will stand with all of our partners all young democracies."

Russian support for reclaiming Crimea majority has intensified amid weeks of relentless state television coverage of purported aggression toward ethnic Russians by the new Kiev government, which came to power after Ukraine's Moscow-friendly President Viktor Yanukovych fled the country in February.

While Putin's ratings have risen since he announced Russia's willingness to use force in Ukraine, the anti-government demonstration Saturday showed that not everyone is happy with the decision.

"I love Ukraine -- it's Putin who needs war and an empire, not me," said Dmitry Maksimov, a 29-year-old lawyer who held a bouquet of flowers dyed blue and yellow, the colors of the Ukrainian flag.

Nadezhda Tolokonnikova, a member of the punk rock protest group Pussy Riot, called for defiance against the authorities.

"Don't believe it when they say that we are few, that we are weak. Together we will change this country," she said in a speech Saturday from a stage.

None of Russia's state-owned news channels showed footage from the anti-government protest, and instead showed live video from the rally near the Kremlin.

The Associated Press contributed to this report.