The federal court in the US has put a block on certain parts of a controversial new immigration law in Arizona.

Sections of the legislation have been suspended, including a provision that requires police officers to determine the immigration status of people they detain.

The law, which will still take effect as scheduled on Thursday, will also be without a provision that would have required immigrants to carry identification papers at all times.

US district judge Susan Bolton ruled that a substantial likelihood that officers would wrongfully arrest legal resident aliens under the new law should cause part of the statute to be struck out.

The judge said the law had been "awkward" in its wording, and that she doubted it could be properly enforced.

Her ruling held that only the federal government, not state governments, should set US immigration policy.

The governor of Arizona said the state would probably appeal the ruling.

She said the law had been passed in April by the Arizona legislature as a necessary step to stop illegal immigration.

The law had been roundly criticised by the US president, human rights groups, the Catholic Church and the Mexican government.

Five percent of the 6.6 million strong population in Arizona are estimated to be illegal immigrants.