The US said that those banned included five politicians and five prominent businesspeople, but would not elaborate.
The decision adds extra pressure on negotiations taking place in Kenya between government and opposition parties trying to find a resolution to the crisis over disputed elections.
Kofi Annan, the former UN chief is leading the talks in the capital, Nairobi, between negotiators for Mwai Kibaki, the president, and Raila Odinga, the opposition leader.
A joint statement on Thursday from the mediation teams said progress had been slow.
'Arming militias'
The opposition has accused the government of arming tribal militias who were involved in ethnic violence in the country.
A Kenyan government spokesman denied the accusations voiced by the secretary general for the Orange Democratic Movement (ODM), saying they were irrational. He warned that they might have undermined dialogue between the two sides.
The joint statement said that addressing the core issue of overcoming the political crisis had "proved divisive at times".
Annan has given 15 days since talks began on January 29 to find a solution.
Political issues are proving to be the sticking points after security and humanitarian issues were initially dealt with.
Separately, Louis Michel, the EU development commissioner, said the opposing parties have showed signs of flexibility in the talks.
Michel, part of an EU delegation currently visiting the capital, held a meeting with the Kenyan president, the opposition leader and Annan and urged them to continue their efforts.
Continued violence
Further clashes have been seen in the northwestern region of Trans Nzoia on Wednesday and into Thursday morning.
Police said that 15 people were hacked to death in an area known for ethnic rivalries before the elections.
That number is added to another 34 people who have died since the start of the week.
Police said their forces killed at least nine people when trying to stop gangs torching properties.
The opposition claims that the December elections were rigged. Since that time, violence has led to over 1,000 deaths and displaced about 300,000 according to the Red Cross.
Ethnic clashes have emerged between Kibaki's tribe, the Kikuyu, and Odinga's Luo tribe.