* American seen staying as head of BP at least until 2020
* BP on course for fastest growth in a generation
* Profit and production rise, heavy debt a concern
* Graphic on oil majors' output: http://tmsnrt.rs/2nGfmte
* Graphic on oil majors' debt: http://reut.rs/2t1h64h
LONDON, June 15 (Reuters) - When BP boss Bob Dudley clinched a final deal to settle litigation over the deadly Deepwater Horizon disaster, many oil industry executives and investors thought his mission was accomplished.
But now, two years later, the 61-year-old is showing no sign of easing into retirement. In fact he plans to oversee an ambitious expansion plan and stay at the helm of the British oil major until at least the end of the decade, according to sources familiar with the matter.
The American CEO has told his leadership team that it is in his family's tradition to not retire until 65 - which would take him to 2020 - and that he could perhaps work even longer than that, the sources said.
In another signal that there is unlikely to be a change at the top anytime soon, there has been no imminent succession planning at the firm, according to the sources, one of who said succession was "not a live project".
When Dudley finally decides to go, there will no shortage of candidates to take his place, however.
BP's chief financial officer, British national Brian Gilvary, 55 and the head of upstream, Irishman Bernard Looney, 46, have been cited as possible successors.
There has been persistent industry speculation about when Dudley will call time on his BP career since he struck the 2015 settlement deal under which the company agreed to pay out a total of about $60 billion over the disaster that left 11 dead and led to the largest oil spill in U.S. history.
He had been made CEO in 2010 - the first American to lead BP in its 108-year-old history - to steer the company through the swathe of U.S. litigation, and the deal represented a milestone.
But rather than stepping back from the fray, he has since embarked on the biggest expansion plan in a generation for BP, even in the face of a collapse in oil prices.
The company has become the fastest-growing oil major in the world. It will launch seven oil and gas fields this year - more than any other year in its history - and will launch nine more before the end of the decade, adding 800,000 barrels per day (bpd) of oil and gas to its production.
By 2020 the company, including its stake in Russian oil giant Rosneft, will be producing as much as 4 million bpd - the same as before the Deepwater Horizon spill and up from the 3 million bpd it was producing after offloading assets to cover the litigation costs.
"We are firing on all cylinders," Dudley told a shareholders meeting in May as he aims to catch up with production volumes of its biggest rivals Exxon Mobil and Royal Dutch Shell .
Whether this strategy will prove effective in the long-term is by no means certain; BP's large liabilities linked to Deepwater Horizon mean it requires a significantly higher oil price - than the present price and compared with rivals - to pay for its operations and dividends. A sluggish recovery in oil prices could also lead to its already high debt rising further.
Rating agency Moody's upgraded BP's credit rating last week for the first time in 19 years while, in another sign of confidence, 97 percent of BP shareholders voted to approve Dudley's new pay package last month.
"Bob hasn't done anything that we wouldn't agree with so far. When times are hard and bad, I would want someone who is pretty sensible and conservative," said Rohan Murphy from Allianz, which holds BP shares.
"Dudley is a safe pair of hands. He won't do anything too maverick," Murphy added. "The recent rating upgrade shows the story hangs together."
The calm and softly spoken Dudley was stress-tested more than once before getting the top job. His career included three punishing years fighting a corporate war with Russian oligarchs at the firm's giant Russian venture TNK-BP that forced him to flee the country and go into hiding.
He became BP chief executive when his predecessor Tony Hayward's tenure ended abruptly following the explosion of the Deepwater Horizon platform in the Gulf of Mexico in 2010.
Dudley was given a task of steadying the ship as BP struggled with a firestorm from the U.S. government, victims of the spill, environmental groups and shareholders.
Over the next five years, the company shed more than $55 billion worth of oil fields, refineries and infrastructure to pay for the spill clean-up.
BP was abandoning low-margin projects and mature markets like Venezuela or Vietnam, often getting top dollar for its sales as oil prices hovered above $100 per barrel.
In retrospect, BP had unknowingly stolen a march on most of its rivals who had to embark on similar asset sales much later when crude prices began to collapse in 2014.
Just as BP was slowly emerging from the spill fallout, the collapse in oil prices drove it to its biggest loss ever in 2016. Like its peers, BP responded by slashing thousands of jobs and tightening budgets.
The efforts bore fruit. In the first quarter of 2017, its profits tripled and its production rose to a five-year high thanks to higher production.
Dudley's team argues that this will only improve over time as the company's strategic change of tack means it is producing more profitable oil and gas from a smaller number of fields.
Another metric investors are also closely watching is BP's debt, standing at $38.6 billion, or 28 percent of its total equity including debt - the highest figure among oil majors.
That ratio is set to improve as Deepwater Horizon cash payments decline over the coming years. They amounted to about $7 billion in 2016 and $4.5 billion in 2017 but will fall to $1-$2 billion from 2018.
BP can currently balance its books only at $60 per barrel, compared to $50 for most of its rivals, but that figure should also fall as Deepwater Horizon payments decline.
"Bob Dudley is building something that could be very interesting in the future ... he just gets on with business and that's what investors want," said James Laing, equities fund manager at Aberdeen Asset Management, which holds BP shares.
"The dividend is still sustainable, debt levels are high but will come down, the cash breakeven has been lowered, the resource base is still increasing," he added. "It doesn't feel like there is a lot of criticism to be made."
(Writing by Dmitry Zhdannikov; Editing by Pravin Char)