TOLUCA, MEXICO - President Obama today condemned the violence occurring in Ukraine and warned there would be "consequences" if the brutality continues.

"The United States condemns in the strongest terms the violence that's taking place. And we have been deeply engaged with our European partners as well as the Ukrainian government and the opposition to try to ensure that that violence ends," the president said shortly after he arrived here for the North American Leaders Summit.

"But we hold the Ukrainian government primarily responsible for making sure that it is dealing with peaceful protesters in an appropriate way, that the Ukrainian people are able to assemble and speak freely about their interests without fear of repression," he said.

"We're going to be watching closely and we expect the Ukrainian government to show restraint, to not resort to violence in dealing with peaceful protesters," the president added. "We've also said we expect peaceful protesters to remain peaceful and we'll be monitoring very closely the situation, recognizing that with our European partners and the international community there will be consequences if people step over the line."

The president made the comments during a bilateral meeting with Mexican President Enrique Pena Nieto.

Jewel Samad/AFP/Getty Images

Months of peaceful protests in Ukraine turned violent this week as thousands of riot police attacked a protest camp in Kiev, leading to clashes that left at least 26 people dead, including 10 police, authorities said.

The White House said today the United States is collaborating with the E.U. to determine whether sanctions should be imposed against Ukraine as violent protests in the country's capital of Kiev continue.

"We continue to watch events very closely including who we believe is responsible for violence, and we have made it clear we would consider taking action against individuals who are responsible for acts of violence within Ukraine," Ben Rhodes, deputy national security adviser, told reporters today aboard Air Force One. "We have a toolkit for doing that that includes sanctions."

In Paris, Secretary of State John Kerry echoed the White House's message.

"We believe the choice is clear and we are talking about the possibility of sanctions or other steps with our friends and Europe and elsewhere in order to create the environment for compromise," Kerry said today.

No one wants #Ukraine to descend into chaos/choice is in President Yanukovich's hands.

- John Kerry (@JohnKerry) February 19, 2014

Vice President Joe Biden spoke with Ukrainian President Viktor Yanukovych on Tuesday to "express grave concern" over the violent clashes in Kiev, the White House said.

"He called on President Yanukovych to pull back government forces and to exercise maximum restraint. The Vice President made clear that the United States condemns violence by any side, but that the government bears special responsibility to de-escalate the situation," the White House said in a readout of the phone call. "The Vice President further underscored the urgency of immediate dialogue with opposition leaders to address protesters' legitimate grievances and to put forward serious proposals for political reform."

ABC News' Kirit Radia and Ali Weinberg contributed to this report.