Factbox-What is the 'Five Eyes' intelligence-sharing alliance?

LONDON (Reuters) - U.S. President Donald Trump's administration announced this week it was suspending intelligence sharing with Ukraine as part of efforts to step up pressure on President Volodymyr Zelenskiy to cooperate with peace talks.

France has said it will continue to offer intelligence to Kyiv, but said it might be difficult for Britain, another of Ukraine's strongest supporters, to do so because of the constraints of the 'Five Eyes' alliance.

Here are details about the alliance: 

- The Five Eyes is made up of Britain, the United States, Canada, Australia and New Zealand which originally evolved from a secret World War Two alliance between British and U.S. cypher and code breaking teams.

In 1946, a signals intelligence agreement was signed between Britain and the U.S. which was later extended to the other three countries.

- It now brings together law enforcement and security agencies from the five members to share intelligence, information and threat assessments across a range of issues relating to national security.

- Its members describe it as the world's oldest and most significant intelligence alliance. All say it is their nation's most important such partnership.

- Working on a basis of a high level of trust, it operates on a presumption that all signals intelligence would be shared with other partners, and that withholding information would be viewed as an exception.

- However, it does not inhibit each nation's intelligence communities from acting unilaterally or choosing not to share information.

(Reporting by Michael Holden, editing by Elizabeth Piper and William Maclean)