Pakistan's ruling coalition has called a session of the National Assembly on Monday after vowing to oust US-backed President Pervez Musharraf, a party spokesman said. “This is the start of the impeachment process,” Farhatullah Babar said on Saturday. The coalition, which swept to power after trouncing Musharraf's allies in February elections, announced Thursday it would seek to impeach the former army strongman, cranking up pressure that he has so far resisted to step down. The coalition accused the president of violating the constitution, bringing “Pakistan to a critical economical impasse” during his eight-year rule, and conspiring against their newly elected government. Babar said the coalition would introduce a resolution to initiate impeachment proceedings. That requires signatures of half of the lawmakers in either the lower house of Parliament – the National Assembly – or upper house – the Senate. If they achieve that, the president, a longtime ally of the US in its war on terror, would have the right to defend himself before Parliament against the charges. Stripping Musharraf of the presidency would then require a two-thirds majority vote of all lawmakers in a joint sitting of the National Assembly and Senate. The coalition claims it has the numbers to achieve this, but Musharraf's allies dispute that. They say Musharraf, who took power in a 1999 coup but has been sidelined from government since the elections, will not quit and plans to fight his ouster. Analysts say that it will be close-run. The coalition appears to fall just short of the numbers required, but could garner the backing of independent lawmakers and defectors from the main pro-Musharraf party. Babar, the spokesman for the largest party in the coalition, would not say exactly when the motion against Musharraf would be moved in Parliament. The coalition says it will first call on the four provincial assemblies to pass resolutions asking Musharraf to seek a vote of confidence in Parliament – a step intended to increase political pressure on him to step down. The constitution states that within three days of receiving a resolution seeking the president's impeachment, the speaker is required to forward it to the president and convene a joint sitting of Parliament between seven and fourteen days later.