Greece warned it was on course to run out of money within weeks if it doesn’t gain access to additional funds, effectively daring Germany and its other European creditors to let it fail and stumble out of the euro.

Greek Economy Minister George Stathakis said in an interview with The Wall Street Journal that a recent drop in tax revenue and other government income had pushed the country’s finances to the brink of collapse.

“We will have liquidity problems in March if taxes don’t improve,” Mr. Stathakis said. “Then we’ll see how harsh Europe is.”

Government revenue has declined sharply in recent weeks, as Greeks with unpaid tax bills hold back from settling arrears, hoping the new leftist government will cut them a better deal. Many also aren’t paying an unpopular property tax that their new leaders campaigned against.

Tax revenue dropped 7%, or about €1.5 billion ($1.7 billion), in December from November and likely fell by a similar percentage in January, the minister said.