WASHINGTON (AP) – Face to face for over two hours, President Joe Biden and Russia's Vladimir Putin squared off in a secure video call Tuesday as the U.S. president put Moscow on notice that an invasion of Ukraine would bring enormous harm to the Russian economy.With tens of thousands of Russian troops massed on the Ukraine border, the highly anticipated call between the two leaders came amid growing worries by the U.S. and Western allies about Russia's threat to its neighbor. Putin, for his part, came into the meeting seeking guarantees from Biden that the NATO military alliance will never expand to include Ukraine, which has long sought membership. The Americans and their NATO allies said that request was a non-starter. There appeared to be no immediate breakthroughs to ease tensions on the Ukraine question, as the U.S. emphasized a need for diplomacy and de-escalation, and issued stern threats to Russia on the consequences of an invasion. Biden "told President Putin directly that if Russia further invades Ukraine, the United States and our European allies would respond with strong economic measures," U.S. National Security Adviser Jake Sullivan said after the call. He added that Biden said the U.S. would also "provide additional defensive material to the Ukrainians … and we would fortify our NATO allies on the eastern flank with additional capabilities in response to such an escalation." That could include additional deployments of U.S. troops to eastern European NATO allies, the adviser said. A top U.S. envoy, Victoria Nuland, said a Russian invasion of Ukraine also would jeopardize a controversial pipeline between Russia and Germany. She told the Senate Foreign Relations Committee Tuesday that if Russia invaded, "our expectation is that the pipeline will be suspended." Putin's foreign affairs adviser Yuri Ushakov dismissed the sanctions threat during a conference call with reporters. "While the U.S. president talked about possible sanctions, our president emphasized what Russia needs," Ushakov said, adding that "sanctions aren't something new, they have been in place for a long time and will not have any effect." He described the presidents' video conference as "candid and businesslike," adding that they also exchanged occasional jokes. In a brief snippet broadcast by Russia state television, the two leaders offered friendly greetings to each other. "I welcome you, Mr. President," Putin said, speaking with a Russian flag behind him and a video monitor showing Biden in front of him.