The election is due to be held in either October or November and Johnson-Sirleaf, 72, is likely to come up against rivals including George Weah, the ex-soccer star who took her to a run-off in 2005.
Opponents say Africa's first elected female head of state is too old to run for a new term and has not done enough to stamp out corruption in a country courted by multinationals for its rich mineral reserves and recent oil finds.
"I am confident that I will win the elections," she told Reuters during celebrations of the anniversary of Liberia's 1847 founding as an independent state.
"I will continue with employment policies. That is why most of the time we encourage private investment. Job opportunities are what we will continue to do," she said in Lofa county, by the border with Guinea and Sierra Leone.
Meaningful figures on employment are hard to come by in West African economies with large informal sectors. However supporters of Johnson-Sirleaf say her government has brought the
unemployment rate down from the 75-80 percent jobless rate common among many of its neighbors to around 55 percent.
Lofa County saw some of the worst fighting in two decades of nearly non-stop civil war that ended in 2003.
Eight years of peace later, Liberia is still one of the poorest countries in the world but has attracted investors including miners ArcelorMittal and BHP Billiton, Malaysia's Sime Darby and U.S. oil major Chevron.
Johnson-Sirleaf has sought to counter the perception of a country that is terminally unstable. During a U.S. trip this year she said the aim was for Liberia to wean itself off foreign aid within a decade and become a middle-income country by 2030.
The United Nations said over 180,000 refugees from the crisis in neighboring Ivory Coast this year fled across the border to Liberia, raising fears that it could destabilize already fragile local communities.
Despite the end of the crisis with the April arrest of former incumbent Ivorian leader Laurent Gbagbo, who had refused to acknowledge losing an election, many Ivorians are too scared to return home and have remained in Liberia.
"I just hope that it will be violence-free," she said of the election, which could go to two rounds if there is no clear winner after the first.
"We want to make sure it is free, fair and transparent and would like for the ballot boxes to be counted on the spot in the presence of all political party representatives, international observers and members of the international community," she said.
Liberian presidential elections have traditionally been slated for October, when the rainy season can make travel and other vote logistics difficult. Voters will be able to decide in an August referendum to delay the election until November.