Belka has been directing economic policy in Iraq since last year

Marek Belka was named as President Aleksander Kwasniewski's choice to replace Mr Miller, who will quit the day after Poland joins the EU on 1 May.

Mr Belka, a former finance minister, has to win the support of parliament.

Correspondents say the main tasks for any new leader will be getting the economy in shape for EU membership.

Marek Belka is a good candidate who can answer challenges facing Poland Aleksander Kwasniewski Polish president

Mr Belka has been in Iraq since last year as director for economic policy for the US-led provisional authority.

He told The Associated Press news agency that he would return to Warsaw on Wednesday to sound out his support among political parties.

Mr Kwasniewski said he had already discussed the candidacy with parliamentary leaders.

"Today, my candidate is Marek Belka," he said. "He is a good candidate who can answer challenges facing Poland."

Mr Belka said he was ready to try to form a cabinet, provided that he had political support for the tough fiscal reforms.

Dissatisfaction

Mr Miller's decided last week to step down from his post after 27 MPs defected from the ruling Democratic Left Alliance to form a rival left-wing party.

He said he was resigning because Polish politics had become too divided and he no longer enjoyed people's trust.

There has been growing dissatisfaction within the party about its declining popularity, currently less than 10%.

The BBC's Adam Easton in Warsaw says the timing of the resignation appears to show Mr Miller has one eye on the history books.

He wants to lead Poland's celebrations as it enters the EU on 1 May, our correspondent says.

High unemployment, a malfunctioning health care system and a string of high profile corruption scandals are seen as the main causes of Mr Miller's unpopularity.

Budget cuts introduced ahead of the country's EU membership, aimed at bringing its economy into line with EU requirements, have contributed to the problems.

Mr Miller stepped down as the leader of his party last month to concentrate on leading the country in the run-up to EU accession.