The Constitution says that Karzai's term ends on May 22 but presidential elections have been set for August 20, raising questions about who should lead the fragile and violence-hit country in the intervening months. Political opponents want Karzai to end his term as laid down in the Constitution and a caretaker appointed, saying their adversary's chances at the polls would be boosted if he held onto the presidency until the vote. Presidential spokesman Homayun Hamidzada told reporters on Tuesday that negotiations were under way to reach a "national consensus" but the government believed there were two options. "First, the issue can be cleared through the Supreme Court and they make a decision based on their independence," he said. "If we cannot get a result this way, then we should resort to the will of the Afghan people and that will be possible through a Loya Jirga." A Loya Jirga is a gathering of both houses of parliament and representatives of provincial and district councils, convened to make the country's most important decisions, including amendments to the Constitution. The UN office in Kabul said the question of what should happen between May and August was "the main political challenge of the moment." "We are looking to Afghan politicians themselves to arrive at the necessary consensus to deal with it," spokesman Adrian Edwards said, stressing the importance of a "fair, credible, transparent" process. "Clearly we don't need, in addition to a difficult security situation, a difficult political situation," Edwards said.