The United States has expressed the hope that the Colombian presidential election on Sunday will be free and fair.

The US ambassador to the United Nations, Bill Richardson, said Washington also hoped that bilateral relations would improve under the future president.

Relations have been strained since 1996 when the State Department barred President Ernesto Samper from entering the United States.

The Clinton administration believes Mr Samper accepted millions of dollars in drugs money for his 1994 election campaign.

He was cleared of the charges by the Colombian congress.

The Colombian security forces are on alert after threats by left-wing guerrillas to disrupt the poll.