Updated

The White House announced Thursday that the U.S. government is imposing visa restrictions on Russians and others who it says are "threatening the sovereignty and territorial integrity of Ukraine," as Congress moves on a separate track to impose more sanctions.

The visa restrictions were placed by the State Department. President Obama also signed an executive order authorizing sanctions against "individuals and entities responsible for activities undermining democratic processes or institutions in Ukraine."

"Depending on how the situation develops, the United States is prepared to consider additional steps and sanctions as necessary," the White House said in a statement.

The new action on visas comes in addition to a U.S. policy denying visas to those involved in human rights abuses related to political oppression in Ukraine. It follows decisions by the Obama administration to suspend military cooperation with Russia, suspend talks on trade and investment and -- more recently -- boost the U.S. NATO presence in the Baltic region.

The White House announcement comes as Western nations have been wrestling with a response to Russia's military incursion into Ukraine's Crimean peninsula. The standoff does not appear to be abating, with Crimean lawmakers scheduling a referendum later this month on whether to join Russia.

Meanwhile, Congress is rushing to put in place hard-hitting sanctions on Russia.The Senate is taking the lead with legislation that would combine loan guarantees to Ukraine's fledgling government and measures against Russian government officials, state-owned banks and companies. The goal of the sanctions is to force Vladimir Putin to withdraw Russian troops from Crimea. The bill could be introduced as early as next week.

House Republicans also have circulated a bill paying for the loan guarantees. The committee will address the resolution Thursday after hearing testimony from State Department and Treasury officials.

Since last weekend, Russian troops have taken control of much of the peninsula on the Black Sea, where ethnic Russians are the majority. Moscow doesn't recognize the Ukrainian leadership that came to power after protesters ousted the country's pro-Russian president last month. Putin and other officials have cited strategic interests as well as the protection of ethnic Russians in making the case for intervention.

The Associated Press contributed to this report.