NAIROBI - The United States hailed the resignation of Kenya's anti-corruption chief and said on Friday it could help drive badly needed reforms after post-election violence last year that rocked east Africa's biggest economy.

Aaron Ringera stepped down on Wednesday and ended a stand-off between President Mwai Kibaki and parliament, which had rejected Ringera's reappointment and threatened to hold up government spending bills over the row.

Critics say Ringera showed little interest in fighting the rampant graft that is a major deterrent to investing in Kenya.

The resignation ... potentially opens the way for more effective leadership of the KACC and thus for significant advancement of the reform process, the U.S. Embassy in Nairobi said in a statement.

The selection of a new director through a transparent and inclusive process will be a further constructive step.

The European Union added its voice to the chorus of complaints about delays to the reform process.

It noted with concern the government's failure to set up a local tribunal to try perpetrators of last year's violence and urged it to end impunity, fight graft and to cooperate fully with the International Criminal Court (ICC) in The Hague.

The ICC has said it is willing to step in and prosecute the masterminds behind the fighting in early 2008.

The European Union will continue to closely follow the situation in Kenya and will consider ways to promote progress on the reforms, Sweden, which holds the rotating EU presidency, said.

The debate over whether Ringera should remain in office had opened further rifts in Kenya's shaky coalition government, which was formed last year to end the post-election turmoil.

Washington sent warning letters last week to 15 prominent Kenyans, including government ministers, members of parliament and other senior officials on both sides of the coalition, who it accuses of blocking the reforms.

It said it might also slap travel bans on some of them.