Anchored by Jake Tapper, The Lead airs at 4 p.m. ET on CNN.
The latest on the crisis in Ukraine, plus why a 700-page book on economic theory is a best seller.
(CNN) – The turmoil in Ukraine has swept aside its president, brought about the release a prominent opposition leader, and raised fears the country could break apart. The country's lightning-speed revolution has ushered in what could be weeks of uncertainty about how the country will pay its way and avoid economic collapse.
Secretary of State John Jerry said that the U.S. wants to work with neighboring Russia on helping Ukraine with the transition.
But some U.S. lawmakers are wary of partnering with Russia.
"I'm very concerned about Russia, especially under Putin. Putin thinks in the context of Peter the Great. Why was Peter great? Because he added more territory to the Russian empire," Sen. Robert Menendez, D-New Jersey, chair of the Senate foreign relations committee.
"I think that's President Putin's views as well, adding more territory to the Russian federation," said Menendez.
Russia's previous actions in Georgia – granting passports to Georgians of Russian descent, and claiming them as Russian citizens in need of protection – could be indicative of the country's plans, says the senator.
"I could see that happening in the Ukraine," said Menendez.
The U.S. and its European allies need to "send a very strong message," says the senator, not only to Ukraine, but also to Putin.
"We need Ukrainians to decide their own future without the intervention of Russia or others. And we need to do that from a position of strength, because if not, Putin won't understand anything but that," said Menendez.
For more of our interview with Senator Robert Menendez, including his views on the so-called "zero option" in Afghanistan, and the growing unrest in Venezuela, check out the video above.