KIEV, Ukraine — Ukraine's president-elect will likely have little trouble wooing Western leaders, including President Barack Obama, when he travels to Poland and France this week — many have already hailed the rise of the pragmatic, Western-leaning leader.

For Petro Poroshenko, who takes office on Saturday, the real task will be grappling with a pro-Russia uprising sweeping Ukraine's east, and a political system dominated by grudging political allies and holdovers from the previous corrupt administration.

That will mean proving to Ukrainians that his government is not a throwback to the corruption and political infighting that have long plagued Ukraine.

"For so long, corruption has been a cost-free, risk-free exercise in Ukraine," said Steven Pifer, a former U.S. ambassador to Ukraine who is now an analyst at the Brookings Institution in Washington.

"While countries can tear themselves up by getting too bogged down in the past and in prosecutions, Poroshenko will have to deal with a lot of public suspicion, because so many of these players have been around for the last 10 years."

After the ouster of Viktor Yanukovych, Ukraine's previous pro-Russia president, following months of protests, he and his closest allies fled the country. But many remnants of the Yanukovych regime stayed behind.

Yanukovych's chief of staff remains in Kiev, along with some of his top security officials during the crisis — when more than 100 people were killed by gunfire in downtown Kiev. The Party of Regions, which backed Yanukovych, has more seats than any other party in parliament and every incentive to stall parliamentary elections until it can regroup from the revolution.

Despite much talk of prosecutions against corrupt Yanukovych-era officials, no charges have been filed against any of those who stayed in Ukraine.

Soon after his election, Poroshenko announced that his first priority would be to clean up parliament, where many legislators are holdovers from the Yanukovych era. While elections aren't due until 2017, Poroshenko, who needs a cooperative parliament to push through direly needed economic reforms demanded by the International Monetary Fund in return for loans, has said he hopes to push that date up to later this year.

"Poroshenko has been told many times that he shouldn't repeat (former President Viktor) Yushchenko's mistakes," said Taras Berezovets, a political analyst at the Berta Communications consulting company, referring to the Ukrainian politician who catapulted to the presidency in the Orange Revolution in 2004 and whose government soon became bogged down by infighting.

"One of Yushchenko's biggest mistakes when he became president was to not call parliamentary elections right away. By the time he did, the economic situation had worsened, people had stopped trusting the government, and he lost."

For Poroshenko, who has little authority in parliament, bringing key players in the legislature fully into his camp may be a struggle. Ukraine's parliament is a notably unruly body, where fistfights sometimes break out.

Poroshenko may even struggle to persuade those players who loudly opposed the Yanukovych government, like acting Prime Minister Arseniy Yatsenyuk or Yulia Tymoshenko, the Orange Revolution heroine and former prime minister noted for her intense rhetoric and ambition.

Tymoshenko — whose Fatherland party is the second-largest faction in parliament — also supports a Western-looking agenda. She has endorsed economic reforms and NATO membership.

But Poroshenko has had a fraught relationship with Tymoshenko in the past, stepping down from a previous position as the head of the national security council after their constant feuding. Tymoshenko received dismal results in the May 25 presidential election, and Fatherland flopped in a simultaneous vote for Kiev city council, leaving her little incentive to push for speedy parliamentary elections.