Opening his party's annual conference in Blackpool, the Liberal Democrat quashed reports he planned to stand down and said he would remain as leader as "long as I feel committed" to the job.
Mr Kennedy is under pressure from senior colleagues to give an impressive performance this week and prove he still has an appetite to lead the party after an election result which failed to deliver several target seats.
As the Tory leadership contender, Kenneth Clarke warned that the Liberal Democrats could eventually overtake the Conservatives, Mr Kennedy urged the Liberal Democrats to show "increasing self confidence" and take on Labour "head to head".
Brushing off questions about whether he would remain as leader, he said: "As long as I feel that I have got something to input in this role for the Liberal Democrats I want to do it and as long as I feel enthusiastic for it, committed to it and I feel we have further achievements ahead that is something I am up for."
Mr Kennedy's leadership will be placed under the spotlight this week when the party debates a proposal by a a senior Liberal Democrat peer to change the rules on nominating a future leader. It would slim down the number of candidates who could run in a contest.
The timing of the move to amend the party's constitution is seen by some as significant because Mr Kennedy has not announced his intention to stand down.
Senior Liberal Democrat figures, including Simon Hughes and Sir Menzies Campbell - who are seen as possible successors to Mr Kennedy - will have a high profile this week.
Mr Kennedy will face his first battle with party activists today when the party debates a motion on Europe which proposes putting a cap of one percent on the EU budget.
Tomorrow the party leadership risks a further clash with grassroots Liberal Democrats over plans to end the monopoly of the Royal Mail and opening up postal delivery to competition.
Yesterday Mr Kennedy faced a call to up the ante on electoral reform and to be more vocal about the need to scrap first-past-the-post voting and replace it with a more proportional system. Speaking at a fringe meeting held by Make Votes Count, ED Davey, the party's education spokesman, said that on PR the party "can't hold back any more".
Praising The Independent's Campaign for Democracy, which calls on Tony Blair to urgently review the voting system, Mr Davey said the current government was "illegitimate" because it failed to gain a majority share of the vote.
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