KABUL, Afghanistan - Under heavy pressure from Afghan lawmakers and Western diplomats, President Hamid Karzai agreed on Saturday to convene the newly elected parliament, ending a political standoff that threatened to spark a constitutional crisis.

After hours of tense discussions at the presidential palace, Karzai backed off his earlier order to delay the session for a month to allow more time for a special tribunal to investigate allegations of fraud in September's parliamentary election, according to two of the lawmakers involved in the talks, Shukria Barakzai of Kabul and Gul Pacha Majidi of Ghazni province.

In return, Karzai asked the parliamentarians to agree that any criminal case against a lawmaker could go forward, said Mirwais Yasini, a representative from Nangarhar province who was deputy speaker of the lower house of parliament in the last session. The legislators agreed to this Saturday evening and drafted a letter to send to the president on today, Yasini said.

While he has not said so publicly, it is generally believed that Karzai is unhappy with the election results and thinks fraud reduced voter turnout among his fellow ethnic Pashtuns. Some of the hundreds of losing candidates said Karzai told them that he believed they were wronged and that he would do everything to support further investigations into election fraud.

The order to delay the parliament, however, sparked an outcry among lawmakers and drew heavy pressure from the United States, the U.N. and other world powers for Karzai to resolve the dispute and allow the 249-seat legislature to get to work.

In a statement released Friday night, the United Nations expressed its "deep concern and surprise" at the president's order for a delay. Siding with the newly elected lawmakers, the U.N., the European Union, the United States, Canada and other nations said they continued to support a "reasonable, enduring and peaceful resolution to this issue" so that the Afghan parliament could convene as soon as possible.

Legislators had threatened to defy the president's ordered delay and start the session on their own today, as originally scheduled, even if they had to meet in a hotel or on the street. Under Afghan law, the president inaugurates the legislature at its opening session.

In an effort to avert a public showdown on Sunday, Karzai invited all the lawmakers to the palace for lunch Saturday and after much debate, a compromise was reached.

"He is coming and Wednesday will be the opening," Barakzai said.

Some politicians, however, were not happy with the outcome, signaling that the political tension could drag on.