Barack ObamaREUTERS/Larry DowningObama makes a statement from the White House Press Briefing Room ahead of a meeting with his national security council.

President Barack Obama addressed a pair of escalating world crises Thursday afternoon, blaming Russia for escalating violence in eastern regions of Ukraine and discussing a strategy he admitted he didn’t “have yet” to confront the extremist group calling itself the Islamic State in Iraq and Syria (also ISIS or ISIL).

His statement from the White House briefing room came amid a day of significant escalation in the crisis in Ukraine, as Ukraine’s president accused Russia of sending troops across the border to fight with pro-Russian separatists in Ukraine’s southeastern regions. Obama said it was clear the ongoing violence had been “encouraged” by Russia, who he said trained and armed separatists in the violence-stricken regions.

“Russia is responsible for the violence in eastern Ukraine,” Obama said. “This ongoing Russian incursion into Ukraine will only bring more costs and consequences for Russia.”

Obama is also scheduled to meet Thursday evening with members of his National Security Council, as well as Vice President Joe Biden, on a strategy to further confront the extremist group ISIS in Iraq and Syria. A White House official said no new decisions are expected on how to proceed Thursday.

“I don’t want to put the cart before the horse,” Obama said, when asked about the next steps in confronting the group.

“We don’t have a strategy yet.”

The U.S. conducted five additional airstrikes against the group in Iraq on Thursday, according to U.S. Central Command. The airstrikes destroyed a Humvee, a tank, four armed vehicles, and a construction vehicle, as well as severely damaging an ISIS checkpoint. Over the past three weeks, the U.S. has conducted 106 airstrikes against ISIS targets in Iraq.

Obama is weighing a broader offensive against the extremist group after it brutally murdered American journalist James Foley. Obama’s secretary of defence, Chuck Hagel, and his top military brass have suggested ISIS needs to be confronted in Syria as part of any plan to contain the group.

Obama said the strategy would need to involve military, political, and diplomatic aspects. He said it would take political reform in Iraq, as well as support from a broad variety of allies in the region to confront ISIS. Obama said he is sending Secretary of State John Kerry to the region to secure allies in the fight, and he has asked Defence Secretary Chuck Hagel to prepare military options to confront the group.

But he said the problem cannot simply be solve through military efforts alone.

“Our military is the best in the world. We can rout ISIS on the ground and keep a lid on things temporarily, but then as soon as we leave the same problems come back,” Obama said.

UkraineREUTERS/Gleb GaranichA Ukrainian Mi-24 helicopter gunship flies above a military base in the eastern Ukrainian town of Kramatorsk August 27, 2014.

The escalation in Ukraine, meanwhile, has sparked international outrage after Ukrainian President Petro Poroshenko accused Russia of sending troops across the Ukrainian border to fight with pro-Russian separatist rebels. Obama said he had spoken with German Chancellor Angela Merkel on Thursday, and he promised additional “costs” on Russia while hinting at the possibility of ramped-up sanctions. But there was one opt oin he ruled out.

“We are not taking military action to solve the Ukrainian problem,” he said.

Earlier on Thursday, United States Ambassador to the United Nations Samantha Power lashed out at Russia in an emergency meeting of the U.N. Security Council. She accused Russia of “outright lies” and a campaign of manipulation.

The emergency meeting of the security council was called after Ukrainian President Petro Poroshenko said Russian troops were fighting on the side of separatists in Ukraine and were advancing in the southeast region of the country. NATO subsequently echoed his allegations.

Ukraine’s defence council said Russian troops are leading a separatist counteroffensive in the east, bringing in tanks and using artillery from inside Ukrainian territory.

A Russian-backed rebel leader said that at least 3,000 to 4,000 Russian troops were fighting inside Ukraine.

This post has been updated with Obama’s comments.

NOW WATCH: Briefing videos

Business Insider Emails & Alerts

Site highlights each day to your inbox.

Follow Business Insider Australia on Facebook, Twitter, LinkedIn, and Instagram.