Islamabad - Pakistan's ruling coalition will move to impeach President Pervez Musharraf on charges of plunging the country into a political and economic crisis, party leaders said on Thursday.

They also warned Musharraf, a former general who first came to power in a 1999 military coup, against any attempt to dismiss the government.

The move is likely to deepen political uncertainty in the nuclear-armed Muslim nation, a key U.S. ally which already faces a faltering economy and a threat from Islamist militants.

The situation has taken a toll on Pakistani markets, with the main share index at its weakest in almost two years and the rupee headed back towards all-time lows posted in early July.

Asif Ali Zardari, widower of slain former prime minister Benazir Bhutto and head of the coalition, said parliament would be called immediately to begin impeachment proceedings.

"The coalition leaders believe that it has become imperative to move for impeachment," Zardari told a news conference with his coalition partner, former prime minister Nawaz Sharif.

Musharraf's spokesman was not immediately available but his allies say he will fight the impeachment.

"We elected him and now we will support him to defeat this move," Kamil Ali Agha, a leader of the main pro-Musharraf party said.

"The president will face the impeachment," he said when asked whether Musharraf had any plans to step down.

The response of the powerful army to the prospect of a humiliating exit for its former chief will be crucial.

Army commanders met in the garrison city of Rawalpindi, close to Islamabad, on Thursday but a military official said it was a routine meeting.

Musharraf seized power as a general in 1999 by toppling Sharif and effectively ruled Pakistan single-handedly for eight years. His position weakened after he stepped down as chief of the army, which has run Pakistan for more than half of its 61 years of independence.

He has become increasingly unpopular at home and lost parliamentary support after his allies suffered a defeat in February elections but he has resisted calls to stand down.

"The economic policies pursued by General Musharraf during the last 8 years have brought Pakistan to the brink of critical economic impasse," a joint statement read by Zardari said.

"He has worked to undermine the transition to democracy."

On the Border

Some analysts say the jockeying for political power has distracted leaders from dealing with Pakistan's economic problems and the effort to control Islamic militants, especially along the border with Afghanistan.

The United States and the Afghanistan government say the border areas are shelters for Taliban and al Qaeda fighters.

Musharraf has previously said he would resign rather than face impeachment. Both Zardari and Sharif warned him against trying to dismiss parliament, as some opposition figures fear.

Under the Pakistani constitution, a president can be ousted if an impeachment motion wins a two-thirds majority of the combined strength of the National Assembly and Senate.

Zardari was confident the motion would be passed with an overwhelming majority.

"We have votes and we also have the courage," he said.

Analysts said while a motion could be tabled this month it could take several weeks before it was put to a vote.

The ruling coalition enjoys a comfortable majority in the National Assembly but the Senate is dominated by Musharraf's allies, though coalition officials claim many of them had assured they would support the impeachment motion.

Shortly before the announcement of the impeachment decision, the foreign ministry said Prime Minister Yousaf Raza Gilani, instead of Musharraf, would leave for China on Thursday to attend opening ceremonies for the Beijing Olympics.

On Thursday, Pakistani stocks had nudged up 0.3 percent, closing at 9,707.29 on turnover of 88.5 million shares, kept in check by anticipation of the formal announcement of the impeachment by the ruling parties.