A spokesman for Finance Minister Wolfgang Schäuble said his government wanted to know quickly whether a European Commission proposal on such a tax could be implemented at EU-level.
"We want to know quickly, as soon as possible, at the latest by the end of the first quarter, whether this is a proposal that works, that can fly, that is worth working on," Martin Kotthaus told a regular government news briefing.
"If not, we need to look to see whether there are other alternatives," he added.
Chancellor Angela Merkel's spokesman hailed a proposal by Economy Minister Philipp Röslerfor a tax on stock market activity as a "clever and sensible" compromise to "bring Britain on board."
However, he stressed the government was still pushing for a financial transactions tax on the basis of the Commission proposal "because it corresponds to our demands for a broad tax with a low rate."
Rösler had earlier proposed in an interview with the Rheinische Post daily that Britain could be persuaded to give up its veto on the financial transactions tax if the other 26 European states followed its model.
"The British already have a special type of stock market tax, the so-called stamp tax," he said.
"If the British cannot move towards the European model of a financial transaction tax, then it would appear sensible to discuss the British model with Britain and other European countries," Rösler said.
Chancellor Merkel will host several top EU leaders next week ahead of a January 30 summit to tackle the euro debt crisis and try to boost the bloc's economy.