Reports say Republican politicians in the United States are considering changing two key provisions in a tough immigration bill passed by the House of Representatives.

It follows a series of large-scale nationwide protests over US immigration policy in recent days.

One of the controversial measures would turn millions of undocumented immigrants into criminals and the other has raised concerns that people who provide them humanitarian relief would be punished by law.

Senior Republicans have now indicated that this was not their intent.

Democrats say Republicans are feeling the heat from the hundreds of thousands of people rallying against the bill.

Senator Edward Kennedy said millions of people had made their voices heard in support of a comprehensive US immigration reform plan and now was the time for action, not empty rhetoric.

Agreement on a Senate bill, which would have to be merged with the House of Representatives legislation, also broke down last week.