Russian President Vladimir Putin said Saturday that his country would not back down from "supporting compatriots" in Ukraine's Crimean Peninsula, which was annexed by Moscow this year despite widespread Western protests.
The Russian Foreign Ministry, meanwhile, said Western sanctions would not force Russia to give up Crimea because the peninsula is a "historic and integral part of Russia." It promised to retaliate against the sanctions.
Putin has remained defiant in the face of the sanctions and a looming recession triggered by falling oil prices and a 40 percent drop in the value of the ruble. On Saturday, as the economic crisis deepened, Putin urged Russians to prepare "to undergo certain difficulties" in the days and months ahead.
President Barack Obama on Friday imposed a wide-ranging trade ban on Crimea through an executive order that bars exports of key U.S. goods and services and blocks Crimean imports.
A White House statement said the order was intended "to provide U.S. clarity to American corporations doing business in the region" and to demonstrate that Washington "will not accept Russia's occupation" of Crimea.
Crimea had been a republic in the former Soviet Union but in 1954 was attached to the Ukrainian Soviet Socialist Republic. Crimea remained part of Ukraine when that country became independent at the breakup of the Soviet Union.
The trade ban includes sanctions on 24 individuals and companies identified as contributing to unrest in Ukraine.
The U.S. measures follow similar moves this week by the European Union and Canada.
Obama on Thursday signed into law a bill authorizing additional sanctions against Moscow for its support of the ongoing pro-Russian rebellion in eastern Ukraine.
Obama said the legislation, known as the Ukraine Freedom Support Act, gave his administration additional flexibility to impose new measures against Moscow "if circumstances warranted."
The law also authorized $350 million in lethal and nonlethal military aid to Ukraine, including anti-tank weaponry, munitions and surveillance drones.
The Kyiv government, the European Union and the United States accuse Moscow of stoking violence in Ukraine and arming pro-Russian separatists seeking autonomy near the Russian border.
Moscow denies arming rebels and insists it annexed Crimea in March only after a referendum showed most Crimeans wanted to become a part of Russia.