Gerhard Schröder has to lose the confidence vote in the Bundestag, or lower house of parliament, in order for new elections to be held, likely in September. He unveiled that plan, to the surprise of almost everyone, after his Social Democratic party suffered a humiliating defeat in the state election in North Rhine-Westphalia on May 22.

The no confidence vote must be tied either to Schroeder's own position as chancellor or to a specific policy of his government -- and that is where the difficulty lies.

If it is turned into a personal referendum on Schröder's leadership, if he does lose the vote, which is the strategy, Schroeder would have trouble justifying his own candidacy in the resulting election battle against likely conservative challenger Angela Merkel, and give the opposition additional ammunition.

Plan B also delicate

The alternative, which is to tie the Bundestag vote to a major policy initiative his government cannot push through, such as a stalled corporate tax cut, is now also proving a delicate matter.

"From a political point of view, given his string of defeats in state elections, Schröder has good reason to call for a no confidence vote," Andreas Falke, a political scientist at Erlangen - Nuremberg University, told Reuters. "But from a purely legalistic standpoint it is difficult for Schröder to find the basis for this vote."

The idea to link it to the tax cut by saying it has been blocked by Schröder's own coalition members, the Greens, has sparked a fierce response by members of the environmentalist party. The Greens agreed to the cut when it was unveiled in March, but have had differences with the Social Democrats (SPD) over financing it.

"We will not be made scapegoats for the no confidence vote," said Krista Sager, Greens leader in the Bundestag. Another party member, Werner Schulz, has vowed legal action if Schröder used "tricks" to get his no confidence vote through parliament.

In calling for an early election even though opinion polls give Merkel's conservatives a 15-21 point lead, analysts believe he was seeking to avoid an embarrassing rebellion by leftists within his own party and to catch the opposition off-guard.

But if the Greens and rebel leftist members of his own party don't play along, Schroeder may have a problem.

Change to constitution?

In a sign of how serious the issue has become, the Berliner Zeitung newspaper reported on Saturday that his allies were contemplating changes to the constitution to ensure the election goes ahead.

The paper reported that Schröder's supporters are seeking to change the constitution to allow the lower house of parliament to dissolve itself ahead of planned early elections. Quoting sources close to the SDP, the paper said the change, which has to be approved by two-thirds of both houses, could be pushed through within four weeks.

At present Germany's President Horst Köhler has the role of dissolving parliament, but legal experts say such a political move does not sit well with his honorific position.

However the parliamentary leader of the SPD's coalition partner, the Greens, Krista Sager, said in a radio interview Saturday she was against changing the basic law "for the needs of the moment."

Designed with the lessons of the unstable pre-Nazi Weimar Republic in mind, the constitution does not allow for the government to dissolve parliament unilaterally and force new elections.

Government sources told Reuters that Schröder's SPD and their Greens partners would meet on Tuesday to discuss a way out of the impasse. Schröder has demanded a solution on the no confidence vote by the end of the week, newspapers said.