NAIROBI (Reuters) - The United States has banned a senior Kenyan government official from visiting the country and may slap similar travel bans on three more people, U.S. Assistant Secretary of State Johnnie Carson said on Monday.

Carson sent letters to 15 prominent Kenyans in September, threatening them with travel bans for blocking political reforms agreed after last year's post-election violence that killed at least 1,300 people.

The move sparked a bitter diplomatic row with President Mwai Kibaki sending a protest note to U.S. President Barack Obama.

The spat was cited as a factor weighing on the Kenyan shilling because it risked hitting the monetary support Kenya receives from its development partners.

"The U.S. government has taken the decision to revoke the visa of a senior Kenyan government official who has been obstructive in the fight against corruption," said Carson.

He declined to name the person, telling reporters just that he was a senior government official "of influence".

"We are considering similar action with three other government officials," Carson told reporters in Nairobi.

Kenya's government spokesman had no immediate comment.