President Obama and other world leaders said Sunday there would be no lifting on the economic sanctions against Russia until it reaches a formal peace agreement with the Ukraine. Obama said they were "standing up to Russian aggression."

The leaders were meeting in the small German town of Garmisch-Partenkirchen for the annual conference of the "Group of Seven" leading democratic industrial powers, also known as the G-7. World leaders from the United Kingdom, Germany, France, Italy, Japan, and Canada, were present. It was the second year in a row Russia was barred from attending.

In a joint press conference with U.K. Prime Minister David Cameron, President Obama said it was important to maintain "the sanctions regime to put pressure on Russian and separatist forces. ... We think that there can be a peaceful, diplomatic resolution to this problem, but it's going to require that Europe, the United States and the Transatlantic Partnership, as well as the world, stay vigilant."

At a separate news conference, European Council President Donald Tusk, who is Polish, agreed the sanctions should stay in place until Russia relents. "Our group is not only a political and economic group of interests, but first of all this is a community of values," Tusk said.

Ukrainian President Petro Poroshenko said last week that they expected more assaults from Russian-allied groups. Five Ukrainian soldiers were killed in clashes Wednesday. European monitors have blamed the unrest on Russia.

Moscow has aided the Ukrainian rebels efforts with supplies and, on some occasions, its own military. It aided the efforts of Crimea-region Ukrainians to rebel in 2014, then annexed the land. World leaders have called the actions illegal and issued the sanctions in return.

The sanctions have boosted inflation in Russia and weakened the Ruble opposite other currencies. Most of the country's economic woes though are likely caused by the steep drop in energy prices, since oil and natural gas being two of Russia's main exports.