The race is on to become the next Taoiseach!
He said he did not see any major failings with Minister Varadkar and his choice was more down to Minister Coveney's attributes and work in the past.
Irish businesses fear Brexit will lead to a costly rise in tariffs, paperwork and transit times.
Fine Gael leadership contender Leo Varadkar. I have chose to implement that decision today.
"He would be a quite capable of leading the party and the other man Leo Varadkar would as well.but I would be sticking my neck out and saying I would be supporting Coveney", he said.
"Enda gave hope to a battered and bruised Ireland in 2011", he said in tribute to Kenny.
"Last year I indicated that I would not lead the Fine Gael Party into the next General Election".
Mr Donohoe described Simon Coveney as "a very fine politician" but said he believed Mr Varadkar had the "rare combination of intellect and judgment needed for leadership".
Setting out his stall he said: "I want to take the country forward".
Fianna Fail leader Micheal Martin praised Mr Kenny's commitment to public service.
The latter alludes to Varadkar's plain-speaking manner, which supporters say could widen the party's appeal.
Athlone Senator Gabrielle McFadden has come out in support of Simon Coveney in the Fine Gael leadership battle, but her party colleage in Westmeath, Deputy Peter Burke, is backing Leo Varadkar.
He has always made himself available to members of the Parliamentary Party and to me at any point, and I have brought up a number of groups from both Longford and Westmeath to meet him in his office to discuss various policy issues. Under Fine Gael rules the parliamentary party commands 65 per cent of the votes, with councillors getting 10 per cent and the 21,000 members 25 per cent.
Athlone's Mayor, Cllr John Dolan, said he was not publicly declaring his support for either candidate.
One of four debates between the candidates is expected to be held in Cork in the coming weeks.
Kenny has asked for a new party leader to be selected, through the Fine Gael leadership election process, by close of business on Friday, June 2.
He advised people not to confuse someone who is good at putting deals together with someone who is weak.
If the two parties can not agree, it would trigger national elections and Kenny would stay in office as head of a caretaker government.
He's also unveiled his election posters and is filing his nomination papers.
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