He said the coordinated actions of the US and European Union would "have an even bigger bite" on Russia's economy.
The new restrictions include banning Americans or people in the US from banking with three Russian banks.
The aim is to increase the cost to Russia of its continued support for pro-Moscow activists in eastern Ukraine.
Moscow denies charges by the EU and US that it is supplying heavy weapons to the protesters.
Speaking at the White House, Obama said the US was widening its sanctions to target the key sectors of the Russian economy - energy, arms and finance.
"If Russia continues on this current path, the costs on Russia will continue to grow," Obama said.
The US Treasury said the banks being targeting in this round of sanctions were VTB, the Bank of Moscow, and the Russian Agriculture Bank (Rosselkhozbank).
Earlier, the EU also adopted new economic sanctions against Russia, targeting the oil sector, defense equipment and sensitive technologies.
This latest wave of US sanctions comes as no great surprise.
For the past few weeks, the US been threatening further action against Russia. It's also been calling for the EU to impose stiffer penalties.
The administration said the tragic events surrounding MH17 should serve as a "wake-up call" to reticent EU countries that something had to be done to curb the actions of Russian-controlled separatists.
President Obama hopes these new measures will apply pressure on President Putin to change his course, something previous sanctions have failed to do so far.
When asked by a reporter if this was the start of a new cold war, Obama said it wasn't. The US-Russia relationship is, in the words of one US official, "complicated".
Full details of the new EU sanctions are expected on Wednesday, when the EU is also set to name more Russian officials facing asset freezes and travel bans in Europe.
German Chancellor Angela Merkel, who had been reluctant to step up sanctions because of Germany's trade links with Russia, said the latest measures were "unavoidable".
Vladimir Chizhov, Russia's ambassador to the EU, told the BBC: "I am disappointed because the EU is slipping along the tracks that lead nowhere.
"I can understand that they are concerned with the situation; so are we, but it's not a prerequisite to impose sanctions."
He added that he believed Ukraine should be subject to sanctions for its role in the conflict in the country's east.
Calls for the EU to act have been fuelled by the downing of flight MH17 over eastern Ukraine. All 298 people on the Malaysia Airlines jet were killed, many of them Dutch citizens.
An international team has again failed to access the crash site, amid heavy fighting between government forces and activists there.
Western governments believe the pro-Russian separatists shot the plane down on 17 July with a Russian missile, believing it to be a Ukrainian military flight. The rebels and Moscow deny that, instead blaming the Ukrainian military.
BA/BA