* Centre-right parties unite against PM
* President Zeman says will keep him in power for weeks even if he loses
* Party leaders want the chance to form new cabinet (Adds quotes from parties)
By Jan Lopatka and Robert Muller
PRAGUE, Aug 7 (Reuters) - The new Czech government formed by allies of President Milos Zeman looked set to lose a vote of confidence on Wednesday, extending a standoff between the president and parliament that has crippled policymaking since June.
Zeman appointed his long-time ally, economist Jiri Rusnok, as prime minister in June despite opposition from the main parliamentary factions, sparking a standoff with the parties who accuse him of breaking democratic customs.
The president, who retains influence with parliament's left-leaning groups, has since secured the support of three parties for the cabinet, but Rusnok remains a handful of votes short of the majority of those present in the 200-seat lower house.
Centre-right parties, whose coalition collapsed in June after criminal charges were laid against a close aide of the then Prime Minister Petr Necas, have 101 votes and reject Rusnok, saying they have the right to form the next administration.
"We are not living in a presidential system, we have not changed the constitution, and so long as this house is elected by the people, the government must answer to this house," said Marek Benda, head of parliamentary faction of the centre-right Civic Democrats.
But Zeman, popular since he was directly elected in January on promises to fight the austerity measures and graft scandals of the former cabinet, said he would keep Rusnok in charge for at least several weeks even if the cabinet loses the vote, expected later on Wednesday.
Markets have so far largely ignored the political standoff, as the country has kept its deficits under control, beating its self-imposed targets despite recession. Debt is at half the EU average and debt yields are by far the lowest in central Europe.
However, the crisis clouds the outlook for the 2014 budget, in which the past and current cabinets planned to ease cutbacks to help revive an economy that has been in recession since 2011.
Rusnok will have to resign if he loses the vote, though he will stay in a caretaker capacity until a new cabinet is formed.
As head of state, Zeman has the sole right to pick the next prime minister, and has no time limit on when he must act, although lawyers say he should act without delay.
The government has already dismissed senior ministry officials and the heads of the state railways, one of the country's largest employers. Rusnok and ministers have also said they would consider changes at supervisory boards of other state and semi-state companies, including electricity firm CEZ .
EARLY ELECTION POSSIBLE
Zeman confirmed he would keep Rusnok in place for several weeks even if he loses the confidence vote, because of police probes into links between politicians and businessmen which contributed to the fall of the previous cabinet.
"I have been assured this investigation will be concluded in several weeks and, I can assure you, even if you put me on the rack I will not make a second attempt (to form a cabinet) during those several weeks," he told parliament.
He drew an immediate protest form the conservative TOP09 party from the centre-right coalition.
"We can do whatever we want as the house...and he will do his own thing and not worry at all about deputies or parliament. That is a clear message," Chairman Karel Schwarzenberg told reporters.
If Zeman's second appointee fails to win a confidence vote, the speaker of the parliament - a post held by the centre-right bloc - would nominate a candidate for prime minister.
Parties could fight Zeman by clipping his constitutional powers. They could also force an early election later this year, before regular polls next May. They would need 120 votes in the lower house to do either, which so far have not been available.
The centre-right, deeply unpopular after years of austerity and graft scandals, has so far opposed early elections that would likely hand power to the left. (Editing by Jon Boyle and David Evans)