AP National Security Writer
WASHINGTON (AP) -- Western powers on Sunday prepared a tough response to Russia's military advance into Ukraine and warned that Moscow could face economic penalties, diplomatic isolation and bolstered allied defenses in Europe unless it retreats.
The crisis may prove to be a game-changer for President Barack Obama's national security policy, forcing him to give up his foreign policy shift to Asia and to maintain U.S. troop levels in Europe to limit Russia's reach.
The ill will and mistrust also could spill over on two other global security fronts -- Syria and Iran -- where Russia has been a necessary partner with the West.
Russian President Vladimir Putin gave no indication that he would heed the West's warnings. Hundreds of armed men surrounded a Ukrainian military base in Crimea, a pro-Russian area. In Kiev, Ukraine's capital, Prime Minister Arseniy Yatsenyuk alerted allies that "we are on the brink of disaster."
Senior Obama administration officials said they believe Russia now has complete operational control over Crimea and has more than 6,000 forces in the region. The U.S. was also watching for ethnic skirmishes in other areas of eastern Ukraine, though the officials said they had not yet seen Russian military moves elsewhere. The officials were not authorized to publicly discuss the situation and spoke on condition of anonymity.
Secretary of State John Kerry said he has consulted with other world leaders, and "every single one of them are prepared to go to the hilt in order to isolate Russia with respect to this invasion." Obama spoke Sunday with German Chancellor Angela Merkel, British Prime Minister David Cameron, and Polish President Bronislaw Komorowski.
Kerry planned to travel to Kiev Tuesday for meetings with the Ukrainian government. Officials said the Obama administration would also focus this week on putting together a package of economic assistance for Ukraine.
The White House issued a joint statement Sunday evening on behalf of the Group of Seven saying the G-7 had suspended participation in the planning for an international summit in Russia this summer. In the statement, the U.S., Canada, France, Germany, Italy, Japan, and the United Kingdom condemned Russia's "clear violation of the sovereignty and territorial integrity of Ukraine." They said Russia's advances in Ukraine violate the "principles and values" on which the G-7 and Group of Eight economic group, which includes Russia, operate.
In Brussels, NATO's secretary-general, Anders Fogh Rasmussen, said Russia's actions have violated a U.N. charter. He said the alliance was re-evaluating its relationship with Russia.
"There are very serious repercussions that can flow out of this," Kerry said.
Beyond economic sanctions and visa bans, freezing Russian assets, and trade and investment penalties, Kerry said Moscow risks being booted out of the powerful Group of Eight group of world powers as payback for the military incursion.
Treasury Secretary Jacob Lew told a Washington audience on Sunday that the United States is ready to work with other countries and the International Monetary Fund to provide support to bolster Ukraine's economy. He said he had been assured in discussions with Ukrainian officials that the new government is prepared to pursue the necessary reforms to overhaul the country's ailing economy.
Lew said that the administration was ready to supplement emergency IMF loans to cushion the impact economic reforms would have on vulnerable Ukrainians.
"The United States is prepared to work with its bilateral and multilateral partners to provide as much support as Ukraine needs to restore financial stability and return to economic growth if the new government implements the necessary reforms," Lew said during a speech Sunday night to the annual policy conference of AIPAC, America's largest pro-Israel lobbying group.
Several U.S. senators also called for bolstered missile defense systems based in Poland and the Czech Republic.
Russia is "going to be inviting major difficulties for the long term," said Kerry. "The people of Ukraine will not sit still for this. They know how to fight."
Still, it was clear that few in the West were prepared to respond immediately to Putin with military force.
At the Vatican, Pope Francis used his traditional Sunday midday appearance in St. Peter's Square to urge world leaders to promote dialogue as a way of resolving the crisis in Ukraine.
Sen. Marco Rubio, R-Fla., discussing the potential of U.S. military strikes against Russian troops in Crimea, said, "I don't think anyone is advocating for that." One of the administration officials indicated that the U.S. was not weighing military action to counter Russia's advances, saying the Obama administration's efforts were focused on political, economic and diplomatic options.