NAIROBI, Nov. 28 (Xinhua) -- A career threatening hamstring injury and loss of form may have drawn the wind out of former world 800m champion Eunice Sum, but the Kenyan runner said here Wednesday that she is back to stake claim to her title.

Ahead of the 2019 season, Sum says she has opted to return to training early to recover lost time having failed to impress in this year.

The hamstring injury limited her competition to just seven the entire season and the proof of her poor form was seen at the Africa Championships in Nigeria where she finished ninth.

Her best run was in Paris Diamond League, meeting where she clocked 1:59.25, but still finished last in the race won by South Africa Olympic champ Caster Semenya.

"Don't rule me out just yet. Last season, I have to admit was very bad for me. Injury and loss of form played a major role in poor performance and that ha triggered me to start preparations early," Sum said.

Now Sum is focused on reclaiming her global title at the world championships in Doha and build on her performance to compete at the 2020 Olympics in Tokyo, Japan.

"The world championship is important to me, just like any other elite runners preparing for the new season. However, I value it higher because I have a challenge to reclaim my title from younger and stronger athletes. It will be a hard shot, which I want to take," she added.

Indeed, younger runners have dominated the field relegating Sum, 30, to the periphery and it will require something special from her talent to creep back to the top.

Semenya leads the rivalry alongside Burundian Francine Niyonsaba and Jamaican prodigy Natoya Goule and American Ajee Wilson.

After winning gold at the 2013 World Championships in Moscow, Russia, Sum failed to defend her title in Beijing two years later and had to settle for a bronze medal before falling at the preliminary stages at the 2016 Olympic Games in Rio, Brazil.

"I value the Olympics and that is the target I want before I retire from this competition. The 2020 Tokyo games are ideal for me and I want to do everything in my power to be fit and contest for the title," said Sum.

To boost her speed, Sum will compete in a few Diamond League races as she builds up for the World Championships, which this time will come late in October in Doha, Qatar.

"I will use the Diamond League in readiness for the World Championships," she added.

Sum will compete in both 800m and 1,500m distances. But for the world championships, she has no doubt to eye 800m title firstly.