BRUSSELS Mon Jan 19, 2015 2:03am EST

Any new Greek government will have to deliver on the commitments of its predecessors and continue reforms, the head of the European Commission Jean-Claude Juncker told Reuters.

His comments are seen as a clear warning to Greece's left-wing Syriza party, which is solidifying its opinion poll lead over the ruling conservatives days before a Jan. 25 election.

Syriza is running on a pledge to end austerity policies, reverse some reforms, stop privatization and renegotiate the country's debt.

"Any future government elected in Greece will have to respect commitments already made and stay the course of reform and fiscal responsibility,” Juncker told Reuters in a statement.

“Europe will stand by Greece. But Europe also expects Greece to stand by its commitments made vis-à-vis its partners."

The national vote will be closely watched by financial markets, nervous that a Syriza victory might trigger a standoff with Greece's European Union and International Monetary Fund lenders and unleash a new financial crisis.