(c) 2014, Bloomberg News.

(c) 2014, Bloomberg News.

WASHINGTON U.S. lawmakers from both parties urged President Barack Obama to lead an international effort to impose diplomatic and economic sanctions on Russia if it attacks Ukraine, though they stopped short of calling for armed intervention.

The reaction preceded a 90-minute phone call between Obama and Russian President Vladimir Putin on Saturday, during which Obama said the U.S. would suspend preparation for an upcoming G-8 meeting in Sochi, Russia, according to a White House statement.

Obama expressed "his deep concern over Russia's clear violation of Ukrainian sovereignty and territorial integrity" in actions Putin's government already had taken, the statement said. And it warned that "Russia's continued violation of international law will lead to greater political and economic isolation."

Following through with a boycott of the G-8 meeting, set for June, and the freezing of assets of senior Russian officials are among further actions that Obama should pursue, the U.S. lawmakers said. Some Republicans said the U.S. and Western European allies also should consider suspending Russia from the G-8, a forum of the world's seven leading industrialized democracies plus Russia.

"President Obama must lead a meaningful, unified response with our European allies to bring an immediate halt to these provocative Russian actions, which threaten international peace and security," Sen. Bob Corker of Tennessee, the top Republican on the Senate Foreign Relations Committee, said on Saturday in a statement.

Sen. Carl Levin, a Michigan Democrat who heads the Armed Services Committee, said one possible specific step that the U.S. and its allies "could take would be to place a significant number of international observers on the ground in Ukraine, if requested by the Ukrainian government."

"The presence of international observers on the ground could reduce the risk that Russia would make a false claim of provocative acts by Ukraine as an excuse for further violation of Ukrainian sovereignty, and thereby help avoid a conflict that nobody should want," Levin said in a statement.

Later on Saturday Samantha Power, the U.S. ambassador to the United Nations, broached the prospect of the deployment of such observers.

"That's the best way to get the facts, monitor conduct, and prevent any abuses," she said at an emergency meeting of the UN's Security Council to discuss the Ukrainian situation.

Sen. John McCain of Arizona, the 2008 Republican presidential nominee defeated by Obama and a member of the Senate Armed Services Committee, called on the president "to rally our European and NATO allies to make clear what costs Russia will face for its aggression and to impose those consequences without further delay."

McCain, who often has pushed for Obama to be more forceful in responding to international crises such as the civil war in Syria, stopped short of calling for military action, though. He said in a statement on Saturday that "there is a range of serious options at our disposal at this time without the use of military force."

The reactions came as Russia's parliament voted to approve military action in Ukraine after Russian troops seized airfields, roads and government buildings in the country's Crimea region. The military movements in Crimea, home to Russia's Black Sea fleet, risk destabilizing Ukraine as its new government negotiates with the U.S. and Europe for financial aid to avoid default.

Russia's moves are "acts of aggression that violate Ukraine's sovereignty and territorial integrity," New York Rep. Eliot Engel, the top Democrat on the House Foreign Relations Committee, said in a statement.

"The United States should work with our European partners to make clear that the violation of Ukraine's sovereignty is unacceptable and ensure that Russia withdraws its troops without delay and refrains from further aggressive actions," Engel said.

At the White House, Obama's National Security Council met to receive an update on the Ukraine situation and discuss potential policy options, the council said in an emailed statement.

While the president didn't attend the meeting, he was briefed by Susan Rice, the national security adviser, and other aides, the National Security Council said in a separate emailed statement.

Obama, in a public statement on Friday, had warned Russia that there "will be costs" if it invades Ukraine, without specifying.

Most U.S. lawmakers, in line with public opinion, are wary of additional U.S. military intervention after more than a decade of wars in Afghanistan and Iraq. Congress was poised to reject Obama's request for military action in Syria last September, though planned votes were scuttled as the U.S. and Russia brokered a deal intended to rid that country of chemical weapons.

A New York Times/CBS poll released Sept. 9 found that 62 percent of Americans said the U.S. shouldn't take the leading role in the world in trying to solve international conflicts. The poll of 1,011 people had a margin of error of plus or minus 3 percentage points. In 2003, by a 48-43 margin, the respondents said the U.S. should take the leading role.

Violence in Ukraine, a major pipeline route for Russian gas to the rest of Europe, escalated in February amid frustration that demands for new elections and broader changes in governance were being ignored. Ukrainian lawmakers deposed Viktor Yanukovych, the former Russian-backed president of Ukraine, on Feb. 22 after clashes with protesters left at least 82 people dead.

Putin is asserting his power over the Crimea region, a part of Ukraine with a large ethnic-Russian population, after Yanukovych's overthrow. Meanwhile, the U.S. has supported Ukraine's new government.

A U.S. official described events over the past days as orchestrated steps intended to make Russian military intervention in Crimea appear legitimate. The official requested anonymity to discuss classified intelligence matters.

In other reactions from lawmakers on Saturday, Rep. Jim Gerlach, co-chairman of the Congressional Ukrainian Caucus, said "any military action Russia takes to reclaim territory would constitute a violation of international law."

Obama should lay out specific diplomatic and economic sanctions "if Russia fails to stand down immediately," the Pennsylvania Republican said.

In a joint letter to Obama on Friday, Senate Foreign Relations Committee members said they would be willing to authorize U.S. loan guarantees to Ukraine. The lawmakers said they "do not seek confrontation with President Putin and his government."

The U.S. "should make use of the tools at its disposal, including targeted sanctions and asset recovery targeting corruption, to dissuade individuals who would foment unrest to undermine Ukraine's territorial integrity or employ coercive economic measures against the Ukrainian people and the new Ukrainian government," said the panel, which is led by Sen. Robert Menendez, a New Jersey Democrat.

Menendez didn't immediately respond to an email on Saturday seeking further comment.

Texas Republican Sen. Ted Cruz was among lawmakers proposing that Obama and European allies remove Russia from the G-8. "If we were serious about standing up to Putin's power grab, we would immediately suspend Russian membership in the Group of Eight, which should consist of nations that can contribute to a civilized order," he said in a statement on Friday.

Joining in that call on Saturday were Sen. Marco Rubio, a Florida Republican, and Rep. Tom Cotton, an Arkansas Republican.

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With assistance from Daryna Krasnolutska in Kiev, Ukraine; Volodymyr Verbyany in Simferopol, Ukraine; Ekaterina Shatalova in Moscow and David Lerman in Washington

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