By Jessica Donati KABUL (Reuters) - As President Hamid Karzai's brothers began a campaign this week to take power in war-shattered Afghanistan, they left open the prospect that the incumbent will be able to use family ties to remain in government after his second term ends next April. Despite the years of feuding that has riven the hugely wealthy clan, the Karzai brothers plan to offer the outgoing president, who is constitutionally barred from running again, a position in their government. "I think he deserves a role," elder brother Qayum, who will stand in the presidential election, told Reuters. "Afghanistan is particularly in need of senior people like the president, who have worked for 13 years to keep the country together." The election is considered the most crucial since the U.S.-led overthrow of the Taliban in 2001, which brought Hamid Karzai to power, and an opportunity to push the country away from years of damaging allegations of corruption and maladministration. Analysts say a successful Karzai family alliance could shield the outgoing president from being pursued over graft allegations. A third brother, the business-minded Mahmoud, will support Qayum's bid to rule the country, seeing an official role for himself too if they win. He agreed that Hamid, the youngest of the three, could play an official role. "My criticism is based on policy, not his personality. Mr. Karzai is a great man. In fact, if we win, he might be our political adviser. We will ask him," Mahmoud Karzai told Reuters in a separate interview. During two terms as president, Karzai has had a rocky relationship with many of his family members, but government officials and analysts still expect him to back Qayum's tilt at the presidency. His siblings have already promised not to investigate allegations of corruption in his administration. "We have pledged not to investigate the past," Mahmoud said. "Move forward, because what has happened has happened, and if you investigate stuff like that, you might create big political problems." CORRUPTION ALLEGATIONS The United Nations has said that last year public sector corruption was worth $3.9 billion in Afghanistan - twice the value of government revenue. Qayum agreed that investigating allegations of past wrongdoing could paralyze the government and declined to say whether the pair would consider investigating their brother. "I do not have an answer to this speculative question. It would be unfair on the president to speculate," he said. The president has said repeatedly that he will not support any one candidate in the election on April 5. But many are unconvinced. "President Karzai cannot openly say that he is actually backing Qayum, fearing uproar from the people and international community," said Kandahar-based analyst Ahmad Shah Spar. "It is impossible to think that Qayum and the president are going separate ways or are from different camps." Allegations of corruption have also swirled around Mahmoud Karzai, a shareholder of the scandal-hit Kabul Bank, which collapsed in 2010 with outstanding loans worth some $1 billion. He has always denied any wrongdoing and said he repayed $22 million. A presidential decree granted immunity to those who returned funds. Qayum Karzai will be competing with a familiar cast of ex-warlords, many of whom fought each other during a civil war that destroyed the capital, Kabul, in the 1990s before the Islamic fundamentalist Taliban seized power. The Karzai name may be a dubious electoral asset for Qayum, 66, but the brothers will be hoping for strong backing from the country's dominant Pashtun ethnic group, to which their clan belongs. "WE'RE DIFFERENT" Mahmoud Karzai said he had differences with the outgoing president and his more moderate elder brother, Qayum. "We are different. We are not the kind of family that you see in a monarchy," he said. "Even in a monarchy you see that one brother slaughters another. It's human nature, we're different." Afghanistan faces an uncertain future, with the NATO-led combat mission due to end next year and increasing Taliban violence in the ethnically riven country. Mahmoud and Qayum made clear they would move away from the testy relationship that the outgoing president has had with the United States over the past decade. Hamid Karzai's increasingly strained relationship with Washington neared breaking point this week when he stood firm on his refusal sign a bilateral security agreement. The deal would dictate, among other things, how many U.S. troops stay in the country after 2014 and what powers they will have. The collapse of a similar pact between the United States and Iraq in 2011 led to the withdrawal of most U.S. forces. The president further distanced himself from U.S. support, declaring bluntly in an interview that the U.S.-led coalition had brought nothing but suffering to Afghanistan. "I would sign it this week. The people of Afghanistan voted unanimously to support the Bilateral Security Agreement ... I don't know what the president is talking about," Mahmoud Karzai said, referring to a decision to put it again to a council of elders that approved it earlier this year. "Three months from now maybe the U.S. will completely change their mind. What are we going to do then? We are not in a position to push to the limit. Without the help, we're nowhere." (Additional reporting by Hamid Shalizi and Mirwais Harooni in Kabul; Editing by John Chalmers and Alex Richardson)