Twenty-five of the European Union's 27 countries have signed up to a new treaty involving tighter fiscal rules, with only Britain and the Czech Republic opposed, EU officials said on Monday.

In a message sent on Twitter, European Council President Herman Van Rompuy said 25 of the 27 members of the union had approved of the treaty - which calls on signatories to introduce a balanced budget rule into national legislation.

An EU official said separately that Britain and the Czech Republic were the two countries staying outside the deal, which is expected to be signed at a ceremony on March 1, when EU leaders meet for their next summit.

British Prime Minister David Cameron made clear at a summit in December that he would not take part.

(Writing by Luke Baker, editing by Mike Peacock)