Washington: The White House was under renewed pressure today as top US lawmakers expressed impatience with Iraqi leader Nuri al-Maliki and called for a withdrawal of US troops to begin.

Republican John Warner, one of the Senate's most influential voices on military affairs, amplified his bombshell demand last week that President George W. Bush should start a limited troop withdrawal from Iraq by Christmas.

"Our troops have performed magnificently, under brilliant leadership, and have done precisely as the president asked," he told NBC television yesterday. "But the government, under the leadership of Maliki and other Iraqi leaders, have totally failed to put the other part of that partnership in place, namely deliver greater security."

Bush last Wednesday defended Iraq's beleaguered prime minister as "a good man with a difficult job," seeking to dispel any sense that Washington is distancing itself from the government in Baghdad.

As pressure mounted on Maliki, top Shiite, Sunni and Kurdish leaders announced in Baghdad they had agreed to resolve key disputes that have aggravated sectarian divisions and plunged the country into political turmoil.

A statement from President Jalal Talabani's office late yesterday said the leaders agreed to ease restrictions on former members of Saddam Hussein's Baath party serving in government ministries, to hold provincial elections, a key demand of Washington, and help security forces in stopping the bloodshed.

The White House quickly seized on the news as an encouraging sign of political progress.