In a new twist to the contentious immigration debate, the Senate has voted to designate English the national language of the United States, and to effectively ban federal government ordinances and services in any language other than English.

The 63-34 vote, on an amendment offered by the Oklahoma Republican James Inhofe, split the Senate along largely party lines, with only nine of the 44 Democrats voting for it, and just one Republican voting against.

The amendment has mainly symbolic significance and may not make it into the immigration bill that eventually emerges from the Senate, let alone into the final version that must be agreed with the House for Congress to send for signature to President George Bush.

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But in a confusing debate passions ran high, with the Democratic minority leader Harry Reid labelling the amendment "racist", and Ken Salazar, a Colorado Democrat of Hispanic ancestry, calling it "divisive and anti-American". Not only does it overrule any claims to multilingual services, but the measure also stipulates rigorous testing to ensure would-be citizens have a sound knowledge of both the English language and US history.

Muddying the waters further, the Senate then passed by a 58-39 margin a more moderate amendment that declares English merely to be the "common unifying language of the US".

The furore over the language proposals are more evidence of how Mr Bush's prime-time address on immigration, when he proposed a "sensible middle way", has failed to bridge the gulf between the two sides.

In his speech on Monday, the President announced the dispatch of 6,000 National Guardsmen to beef up controls along the 2,000-mile US/Mexico border, but also urged a mechanism that would permit long-term illegal immigrants to apply for citizenship.

The aim was to offer enough sticks to placate conservatives, and enough carrots to satisfy the pro-immigrants, thus consolidating support among Hispanics which Republican strategists see as a key part of a long-term majority for the party in US politics.

But the Republican right is still outraged by what it considers "amnesty" by another name, and party leaders in the House have vowed to block any such provision. The bipartisan measure now under debate in the Senate allows a guest-worker programme - capped at 200,000 a year - and provides for illegal immigrants who have been here for at least five years to embark on the road to citizenship.

The pro-immigrant lobby is increasingly worried about the rightward tilt of the debate. The Senate passed a separate amendment this week backing construction of a 370-mile-long "fence" along the border, and the move to formally designate English as America's national language is seen as yet another gambit by immigration foes to toughen the final bill.

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Even so, the Senate version is far less harsh than the measure passed by the Republican-controlled House of Representatives. This contains no procedure leading to citizenship, would turn the border into a quasi-militarised zone, and impose tougher sanctions on illegal immigrants and those who employ them.

The linguistic melting pot

* Legend has it that English only defeated German by a single vote to become the official language of the United States, in a 1795 Congressional debate.

* Until now, America has never had an official language. Before World War I, more than 6 per cent of US primary school children were taught in German. More than 45 million Americans say their ancestry is German.

* Mass immigration throughout the 20th century means 336 languages are currently in use, including 176 indigenous dialects.

* Over 47 million Americans speak a language other than English at home. Spanish speakers make up just under 30 million of that total.