The U.S. and European Union on Friday leveled a new round of sanctions aimed at Russia over its role in the ongoing crisis in Ukraine, targeting Russia's largest bank and a major defense conglomerate.

These new sanctions further escalate diplomatic tension between the West and Russia. They come at a delicate time — Ukraine's government and pro-Russian separatist rebels in Ukraine's eastern regions are a week into a cease-fire that has mostly held despite accusations of violation by both sides.

The latest U.S. sanctions, an expansion of the previous round, target Russia's financial, energy, and defense sectors. Among the new targets is Russia’s largest bank, Sberbank of Russia, as well as the major defense conglomerate Rostec.

The sanctions prohibit U.S. citizens or companies from providing new financing to Sberbank, thereby cutting off its access to U.S. capital markets. The sanctions also shorten the maturity threshold for the debt prohibition to 30 days from 90 days — meaning U.S. persons cannot provide equity or debt financing of longer than 30 days.

The new measures "will significantly increase the pressure on these institutions by constraining the financing options available to them," a senior administration official said Friday.

The U.S. has now targeted Russia's six largest banks in sanctions — Bank of Moscow, Gazprombank OAO, Russian Agricultural Bank, Sberbank, VEB, and VTB Bank.

The sanctions also are aimed at Rostec, a major Russian defense conglomerate. Like the restrictions on transactions with Russian banks, the new sanctions restrict U.S. loans to Rostec to no more than 30 days' maturity.

And the new measures prohibit U.S. companies from exporting goods, services, or technology to support five Russian energy companies in exploration or production for Russian deepwater, Arctic offshore, or shale projects that have the potential to produce oil. The Russian energy companies hit by the sanctions include Gazprom, Gazprom Neft, Lukoil, Surgutneftegas, and Rosneft.

A senior U.S. official said the new sanctions were designed to "effectively shut down" Russia's offshore, Arctic, and shale oil exploration.

U.S. President Barack Obama said Friday that the sanctions were being imposed in response to Russia's "actions to further destabilize Ukraine over the last month," including an incursion of at least 1,000 Russian forces into eastern Ukraine to fight with pro-Russian separatists in eastern regions of the country. The president also said a cease-fire reached last week has not produced "conclusive evidence" Russia has worked to de-escalate the crisis.

"I encourage President Putin to work with Ukraine and other international partners, within the context of the Minsk agreement and without setting unreasonable conditions, to reach a lasting resolution to the conflict," Obama said in a statement.

"As I said last week, if Russia fully implements its commitments, these sanctions can be rolled back. If, instead, Russia continues its aggressive actions and violations of international law, the costs will continue to rise."

Speaking in Moscow, Russian President Vladimir Putin said the new sanctions were "quite odd" in light of the cease-fire agreement. He said Russia would consider retaliatory measures but that he also found there to be more good than bad in Russia's current situation.

"There are some things that are negative, but if we consider the problem in its totality, there is more positive than negative," Putin said.