The United States is the world's most unfriendly country for international travellers, a survey suggests.

The global survey showed the US was ranked "the worst" because of rude immigration officials and long delays in processing visas.

More than half of the travellers surveyed said US immigration officials were rude and two-thirds said they feared they would be detained on arriving in the US for a simple mistake in their paper work or for saying the wrong thing to an immigration official.