DAVOS, Switzerland — Ukraine's president showed no mercy Friday for imprisoned former Prime Minister Yulia Tymoshenko, despite increasing fears that her case will hurt his country's struggling economy and its relations with the European Union.

The gas contract with Russia that was the premise for Tymoshenko's conviction "is Ukraine's biggest problem today," President Viktor Yanukovych said at the World Economic Forum in Switzerland. He added that he foresaw more judicial troubles for the ex-premier.

Tymoshenko, a bitter rival of the current president, is serving a seven-year sentence on charges of abuse of office in a case the West has condemned as politically motivated. Her family accuses prison authorities of denying her proper medical care.

Tymoshenko was found guilty last year of overstepping her authority while negotiating the natural gas import contract with Russia in 2009. Authorities say the contract was not in Ukraine's economic interest. She charges that Yanukovych ordered her imprisonment to bar her from elections.

Yanukovych's presence at the forum in Davos was aimed at attracting investment from international CEOs at the invitation-only event, but his comments about Tymoshenko did little to soothe concerns about doing business in Ukraine.

Ukraine "cannot hope to attract investment if the law doesn't apply," Swedish Foreign Minister Carl Bildt said. He said a landmark cooperation deal between Ukraine and the EU is "dead in the water" as long as Tymoshenko is jailed.

But Tymoshenko's jailing is a dilemma for the EU. Some experts believe that the bloc should not be partners with a government that throws opposition leaders in jail. Others say snubbing Ukraine would push it back under Russia's influence as Kiev courts Moscow for cheaper natural gas.

Tymoshenko rose to fame during Ukraine's 2004 popular uprising. She became an opposition leader after losing the premiership in 2010.

Yanukovych has made membership in the 27-nation EU a top priority, but exhibited little sign Friday that he was ready to concede on the Tymoshenko case.

The state security service has launched a slew of new criminal investigations against Tymoshenko since her conviction, probes that Yanukovych defended.

"The Ukrainian part of the crimes committed by people who were in one way or another connected to Tymoshenko have not been fully investigated," he said, adding that the cases will go to court soon.

Yanukovych was cold to efforts to adopt changes to the criminal code that would allow the former prime minister to be freed. "That is up to the parliament," he said. The parliament is dominated by his supporters.