President Obama spent much of his weekend on the phone, talking with allies about some kind of unified response to Russian military aggression in Ukraine.
"The leaders expressed their grave concern over Russia's clear violation of Ukrainian sovereignty and territorial integrity," said a White House statement Sunday after Obama spoke separately with British Prime Minister David Cameron, Polish President Bronislaw Komorowski, and German Chancellor Angela Merkel.
Saturday's call list for Obama featured French President Francois Hollande and Canadian Prime Minister Stephen Harper.
The White House statement Sunday called Russia's actions "a breach of international law and a threat to international peace and security."
The allies' options are limited -- no one is talking about military intervention in Ukraine -- but include economic sanctions on Russia, aimed at President Vladimir Putin.
There is also talk about visa bans, freezing Russian assets, trade and investment penalties, and kicking Russia out of Group of 8 international meetings. The U.S. and other countries have scrapped preparation meetings for a June G-8 summit in Russia, and may boycott the summit itself.
The United States and its allies pointedly identified themselves as the "G-7" in a statement condemning Russia's actions.
"We call on Russia to address any ongoing security or human rights concerns that it has with Ukraine through direct negotiations, and/or via international observation or mediation," said a statement signed by the U.S., Canada, France, Germany, Italy, Japan, and the United Kingdom.
Obama and allies are also talking about increased financial assistance to Ukraine's democratic government.
In calling for "unity within the international community," the White House statement cited Ukraine's plans "to move forward with elections in May so that the Ukrainian people can continue to determine their own future in this historic hour."
Secretary of State John Kerry is traveling Monday night to Ukraine. Kerry, Defense Secretary Chuck Hagel, and Treasury Secretary Jack Lew have been in contact with counterparts from Ukraine, Russia, and other nations.
As he seeks to work with other leaders, Obama faces some criticism at home from Republicans who say a weak U.S. foreign policy has emboldened Putin and Russia.
"Every time the president goes on national television and threatens Putin, or anyone like Putin, everybody's eyes roll, including mine," said Sen. Lindsey Graham, R-S.C., on CNN's State of the Union. "We have a weak and indecisive president that invites aggression."