VIENNA (AP) — A 57-nation organization with a history of mediation but no enforcing powers has been tasked with helping to translate diplomatic progress on easing Ukrainian tensions into reality on the ground.

A special team of the Organization for Security and Cooperation in Europe "should play a leading role" in immediately implementing "de-escalation measures wherever they are needed most," according to an agreement Thursday between Russia, Ukraine, the U.S. and the European Union.

That means primarily eastern Ukraine, where pro-Russian insurgents occupy government buildings in more than 10 cities. But the OSCE special mission to Ukraine has no muscle to enforce its vague mandate, limiting it to advisory and monitoring roles.

A look at the organization, its role in Ukraine and what it hopes to achieve there:

____

WHAT IS THE OSCE?

The OSCE began as the Conference on Security and Co-operation in Europe in the early 1970s to build on the detente between the superpowers and their blocs of influence. Despite its name, the organization also includes Russia, the U.S., Canada and some central Asian nations.

Since changing its name in 1994, it has tried to respond with dialogue and mediation to Europe's post-Cold War challenges of nationalism, ethnic hatreds and resulting local conflicts.

Its Permanent Council makes decisions by consensus. But other OSCE branches have a measure of independence to investigate human rights, minority issues and related topics on their own.

____

WHAT HAS ITS ROLE BEEN IN UKRAINE?

Unarmed OSCE military observers from member countries were repeatedly blocked from visiting Crimea between March 5 and March 20, as the peninsula veered into Russia's orbit.

The teams were sent at the request of Ukraine outside the OSCE consensus rule and didn't require Russian approval. They were prevented from entry into Crimea by pro-Russian units, including some who fired warning shots, but were able to report that such units apparently included regular Russian military troops.

___

WHO MAKES UP THE TEAM?

The 100-strong team tasked in Geneva to "play a leading role" in reducing tensions between Ukrainian and Russian ethnic groups in the east includes personnel from Russia and the U.S. and can be expanded to up to 500 people. It was established March 21, and has been observing and reporting to the OSCE Permanent Council on the situation in Ukraine since then.

___

WHAT POWERS DOES IT HAVE?

With its role specifically endorsed by Russia at the Geneva meeting on Thursday, the monitoring team is expected to seek to mediate between pro-Russian insurgents in the east and local authorities. Still, refusal by pro-Russian groups to vacate buildings they hold despite the Geneva meeting indicates a tough road ahead. Moscow may well have to step in and specifically direct individual insurgent groups to cooperate with the OSCE team.

Moves by Ukrainian nationalists also play a role in whether OSCE mediation will work. Russian Foreign Minister Sergey Lavrov on Thursday emphasized the requirement to abandon occupied building applied to all parties — an apparent reference to the ultranationalist Right Sector, whose activists are occupying Kiev city hall and a Kiev cultural center.

___

WHERE WILL IT DEPLOY?

The mission has been in Ukraine since last month and is logistically well-placed to move quickly where it is needed. That is sure to include the 10 eastern cities where pro-Russian nationalist are occupying buildings, including the Donetsk headquarters of the self-styled Donetsk People's Republic. It will also work in Kiev with Ukrainian authorities to defuse tensions with the Right Sector and their occupation of buildings.

___

WHAT ELSE IS THE OSCE DOING?

The OSCE has begun to send election monitors to Ukraine before the May 25 presidential election. The team, which could reach up to 900 members by election day, will report on any irregularities in the vote.

An OSCE rights mission met with officials and Russian and Ukrainian minority communities throughout Ukraine, including Crimea, between March 18 and April 1, and will soon release a report on its findings. The OSCE High Commissioner on National Minorities, Astrid Thors, visited Ukraine, including Crimea, several times in March and April.

OSCE media freedom chief Dunja Mijatovic visited Crimea as well as Kiev in early March and Kiev in April. The OSCE describes her role as providing "early warnings on violations of freedom of expression and media freedom." She has issued critical statements about the safety of journalists since the crisis broke.

At the request of Ukraine, a 15-member team of experts has been deployed in areas of Ukraine outside of Crimea to "support confidence building between different parts of Ukrainian society."