Clinton's chief strategist quits

Mark Penn will continue as a pollster and adviser for Mrs Clinton

The chief strategist for Hillary Clinton's campaign to become the Democratic Party's candidate for the US presidency has resigned.

Mark Penn stepped down after a row over a potential conflict of interest involving his public relations firm.

Mr Penn's company had been employed by the Colombian government to help it pursue a free-trade agreement with the US - a deal Senator Clinton opposes.

She is competing against Senator Barack Obama for the Democratic nomination.

They have been fighting a close battle in the continuing state primary election campaign.

The latest count of pledged delegates to the party's national convention in August, according to Associated Press, puts Mr Obama at 1,634 and Mrs Clinton at 1,500.

A total of 2,024 delegates is needed to win the Democratic nomination.

Union opposition

In a statement, Mrs Clinton's campaign manager, Maggie Williams, said Mr Penn had stepped down after it was disclosed he had met Colombian officials seeking his help to push the Colombia Free Trade Agreement through Congress.

The meeting was an error in judgment that will not be repeated and I am sorry for it Mark Penn

"After the events of the last few days, Mark Penn has asked to give up his role as chief strategist of the Clinton campaign," she said.

She said he would "continue to provide polling and advice to the campaign".

Mrs Clinton's communications director, Howard Wolfson, and pollster Geoff Garin will take over co-ordinating her "strategic message team", Mrs Williams added.

The Wall Street Journal reported on Friday that Mr Penn had met the Colombian ambassador to the US on 31 March in his capacity as chief executive of the public relations firm, Burson-Marsteller, to promote US approval of the trade accord.

Mr Penn later issued a statement apologising for attending the meeting, calling it an "error of judgement that will not be repeated".

His words were not, however, well received by the Colombian government, which said it considered the "declaration a lack of respect towards Colombians, which is unacceptable" and reportedly fired the PR company.

The deal is opposed by unions, whose support is essential for Mrs Clinton

The US government completed the Colombia Free Trade Agreement in 2006 and is seeking approval in Congress. The pact would eliminate tariffs on flowers, corn, machinery, meat and other products and also set rules for investment.

A BBC correspondent in Washington says the free trade deal is opposed by US trade union leaders, whose support is essential for Mrs Clinton.

Mr Penn is not the first senior Clinton adviser to have resigned in recent months.

Geraldine Ferraro stepped down from an honorary role on Mrs Clinton's finance committee three weeks ago after she said Mr Obama would not be where he was in the race for the White House if he were not black. Patti Solis Doyle quit as her chief of staff in February.