President Obama tried to ratchet up the pressure on Moscow to stop supporting pro-Russian separatists in Ukraine on Wednesday by announcing new sanctions against several large banks, energy and defense firms in the country.

The moves only limit sectors of Russia's economy from the U.S. marketplace and don't cut them off entirely. But they go much farther than the administration's sanctions so far, which have placed financial and travel limits on several dozen Russian individuals and their businesses.

Over the past several weeks, the Russian government has chosen to escalate its support for pro-Russian separatists in Ukraine and has failed to engage in internationally mediated talks, Obama said.

"These sanctions are significant, but they are also targeted and designed to have the maximum impact on Russia while limiting any spillover effects on American companies or those of our allies," he told reporters gathered in the White House's Brady press room.

"So far, Russia has failed to take any of the steps that I mentioned. In fact, Russia's support for the separatists and violations of Ukraine's sovereignty have continued," he said.

The Treasury Department's actions prohibit any U.S. individual from providing new financing to two major Russian financial institutions, Gazprombank and VEB, along with two Russian energy firms, Novatek and Rosneft.

It also extended the same prohibitions to eight Russian arms firms responsible for the production of a range of small arms, mortar shells and tanks, four Russian government officials, an oil shipping facility in Crimea and the pro-Russian separatist leader operating in Ukraine and rebel groups in the eastern cities of Luhansk and Donetsk.

The actions, however, do not limit all U.S. transactions with the banks. Instead, they bar individuals in the U.S. from engaging in transactions or providing financing for any new debt of longer than 90 days maturity or new equity.

“As a practical matter, this step will close the medium- and long-term U.S. dollar lending window to these banks, and will impose additional significant costs on the Russian government for its continued activities in Ukraine,” said an administration official.

Obama said his administration is coordinating the new sanctions with European leaders, who are meeting in Brussels on Wednesday to hash out their own set of new penalties on Russia. They aren't expected to take as strong of actions as the U.S., opting instead to prevent any new loans from European banks to Russia.

In making his statement on the new sanctions, Obama also weighed in on several other thorny foreign policy matters.

He thanked Secretary of State John Kerry and military leaders in Afghanistan for their help breaking an impasse over the recent contested presidential election. He said both candidates, Abdullah Abdullah and Ashraf Ghani, have agreed to abide by the results of an internationally supervised audit of the election results.

"If they keep their commitments, Afghanistan will witness the first democratic transfer of power in the history of that nation," he said.

He also addressed the status of the nuclear talks with Iran. An interim six-month agreement ends July 20 and Kerry and his Iranian counterparts are contemplating extending the deadline in order to continue negotiations on a more concrete, long-term agreement.

Obama said Iran had "met its commitments" over the last six months, halting progress on its nuclear program, allowing more inspections and rolling back its most dangerous stockpile of nuclear material.

Citing "real progress" on the Iranian nuclear issue, Obama said he would continue to consult with Kerry and others to determine whether the July 20 deadline should be extended.

When it comes to the recent violent clashes between Israel and Hamas, Obama said Israel retains the right to defend itself and said he's proud that the U.S.-supported Iron Dome system has helped save Israeli lives.

Still, he said, "we've all been heartbroken" by the deaths of so many innocent civilians in Gaza — men, women and children — who have been caught in the crossfire.

Over the next 24 hours, he said, "we'll continue to stay in close contact with our friends and parties in the region. And we will use all of our diplomatic resources and relationships to support efforts of closing a deal on a cease-fire."

"In the meantime, we're going to continue to stress the need to protect civilians in Gaza and in Israel and to avoid further escalation," he said.