Nigeria's leader Goodluck Jonathan has said he will ask MPs to amend the constitution so that future presidents serve a single, longer term in office.The constitution currently limits presidents to two four-year terms.There has been speculation in Nigerian newspapers that the proposed amendment would enable President Jonathan to extend his term in office.But the president, who is at the start of a four-year term, said it would not come into effect before he steps down."If the proposed amendment is accepted by the National Assembly, the president assures that he will not in any way be a beneficiary," AFP quotes a statement from Mr Jonathan's office as saying.Mr Jonathan did not specify how long the new term should be, but he said the change would focus politicians more on governance and less on re-election.The BBC's Jonah Fisher in the commercial capital, Lagos, says it is thought the new single term would be for six years.The statement said Mr Jonathan "was concerned about the acrimony which the issue of re-election every four years generates".An estimated 500 people were killed, thousands of people forced from their homes and some mosques and churches set on fire after the announcement of April's election results."The nation is still smarting from the unrest, the desperation for power and the overheating of the polity that has attended each general election," said the statement.Mr Jonathan, a Christian from the oil-producing Niger Delta, was appointed to the presidency last year upon the death of incumbent Umaru Yar'Adua, a northern Muslim whom he had served as vice-president.He won April's election with nearly 60% of the vote.Source: BBC