Berlin  - German Chancellor Angela Merkel seems poised to win Germany's parliamentary election on September 27 - but the make-up of a future coalition in Europe's largest economy hangs in the balance.

Opinion polls have consistently put the chancellor's conservative alliance well ahead of its nearest rival, the centre-left Social Democrats (SPD) of Foreign Minister Frank-Walter Steinmeier.

Merkel wants to jettison the Social Democrats after four years together in an uneasy grand coalition and replace them with the more business friendly Free Democrats (FDP), led by Guido Westerwelle.

Polls hover around 50 per cent in favour of such a "black-yellow" coalition (named after the respective party colours of the CDU and FDP), but a last-minute swing could deprive the chancellor of a majority and force her to shop around for a third partner.

"Floating voters may decide the outcome," said Thomas Petersen from the research group Allensbach, pointing out that one-quarter of those who cast ballots make up their minds at the last moment.

Six parties are expected to make it into the lower house, or Bundestag: Merkel's Christian Democrats (CDU) and their Bavarian sister party CSU, the SPD, FDP, Greens and the Left Party.

After a generally lifeless election campaign, the CDU has a lead of more than 10 per cent over the SPD, its nearest rival, while Merkel's personal popularity outstrips that of Steinmeier by more than two to one.

"Voters see her as more sympathetic and having greater self- assertion," said pollster Forschungsgruppe Wahlen of the person declared by the US magazine Forbes to be the world's most powerful woman.

Merkel, a pastor's daughter who grew up in communist East Germany, became the country's first female chancellor when she defeated Social Democrat Gerhard Schroeder in 2005 elections.

The Christian Democrats have tailored their campaign around Merkel, whose undemonstrative leadership style and steady hand have helped stabilize the economy during the worst recession in six decades.

Her reputation as a crisis manager was further enhanced when her strategy for a state-sponsored rescue of Opel was approved by the ailing carmaker's US parent General Motors after months of debate.

The CDU has proposed tax cuts as a means of promoting growth, while Steinmeier sought to raise his economic credibility with a programme designed to create 4 million jobs over the next decade.

The two parties hold similar views on Germany's involvement in Afghanistan, which became a late campaign issue after an airstrike ordered by German troops on stolen fuel tankers claimed more than 90 lives.

But differences remain over nuclear energy, with Merkel's party pledging to extend the life of reactors due to be phased out by 2020, while the SPD wants a complete shutdown of atomic power by this date.

Merkel's policy on nuclear energy is backed by the Free Democrats, but opposed by the environmentalist Greens, a potential third partner in a broader coalition dubbed Jamaica because the parties' colours are the green, black and yellow of the Jamaican flag.

"Merkel would have to make concessions on nuclear energy and the distribution of cabinet posts if it does come to talks on such a coalition," said Scott Stock Gissendannar, a political scientist at the University of Goettingen.

An outside possibility is a so-called traffic-light coalition that would see the red of the SPD replace the CDU in a three-way alliance with the Greens and FDP.

Such a solution, favoured by the SPD, would enable the FDP to return to government after 11 years in opposition if its other coalition options fall through.

If neither of the two major parties achieves their desired goal, there is always the possibility of resuscitating the grand coalition, although both Steinmeier and Merkel say they are against such a move.

In their only televised debate, which commentators said was more of a duet than a duel, the two rivals appeared to leave the door open by praising their work together over the past four years.

Some 62 million voters are eligible to cast ballots in the election, which comes less than two months before Germans celebrate the 20th anniversary of the fall of the Berlin Wall. (dpa)