WASHINGTON, July 16 - U.S. President Barack Obama on Wednesday announced the most wide-ranging sanctions yet on the Russian economy, targeting key institutions including Gazprombank and Rosneft Oil Co, as well as other energy and defense companies, Reuters reported.

Washington has steadily escalated its financial sanctions on Russia over what it views as Moscow's interference in its neighbor Ukraine and its annexation of the Crimea region. Obama said the United States could impose further sanctions if Russia did not take concrete steps to ease the conflict.

The targeted companies also include Russia's second-largest gas producer, Novatek, Vnesheconombank, or VEB, a state-owned bank that acts as payment agent for the Russian government, and eight arms firms.

The U.S. Treasury Department, which posted the sanctions on its website, said the measures effectively closed medium- and long-term dollar funding to the two banks and energy companies. But the sanctions did not freeze those four companies' assets.

The sanctions stopped short of targeting Russia's Gazprom, the world's largest natural gas producer and provider of much of Europe's energy supplies. Gazprombank is 36 percent-owned by Gazprom.

"These sanctions are significant, but they are also targeted, designed to have the maximum impact on Russia while limiting any spillover impact on American companies or those of our allies," Obama told reporters.

The new measures were announced on the same day that European Union leaders met in Brussels and agreed to expand their own sanctions on Russia.

The new U.S. sanctions also include Feodosiya Enterprises, a shipping facility in Crimea, and senior Russian officials, several of whom had already been targeted by the European Union.