Russia reluctantly agreed to the deployment of international monitors in Ukraine following ominous warnings from Washington about the Kremlin's massing of thousands of troops along the country's south-eastern border.
The monitors were set to fan out across Ukraine, except Crimea, as US President Barack Obama was scheduled to meet world leaders in The Hague tomorrow. His trip to Europe was originally to focus on trade and nuclear security but is now expected to turn into a mission to mobilise international opposition to Russia's annexation of Crimea last week.
The West is concerned that Russian President Vladimir Putin may push further into the former Soviet republic. In response, European leaders last Friday followed the United States' lead in levying financial and travel restrictions on members of his inner circle, and warned Moscow it may face further repercussions.
German Foreign Minister Frank-Walter Steinmeier said in Kiev yesterday - after what he called "difficult" talks with Moscow - that the European Union (EU) also hopes the presence of monitors will help avoid escalation of the crisis.
The Vienna-based Organisation for Security and Cooperation in Europe (OSCE) said yesterday that it will initially send in 100 monitors across Ukraine, except for Crimea, and that number may increase by 400.
Their six-month mission is meant to cool tensions in the worst stand-off between Russia and the West since the end of the Cold War.
Swiss Foreign Minister Didier Burkhalter, the chairman of the 57-nation group, said that the OSCE will try "to rebuild bridges and find cooperative solutions to the major political and security challenges that Europe is now confronted with".
In The Hague tomorrow, Mr Obama is scheduled to meet leaders of the EU, China, Japan and other nations. White House National Security Adviser Susan Rice told reporters in Washington last Friday that the US is focusing on diplomatic and economic tools to defuse the crisis.