Greece will need 4 billion euros for debt servicing in first quarter: ESM head

Some euro zone officials expect Greece to get creditors' approval on reforms as soon as February, but others, such as euro zone finance ministers' chairman Jeroen Dijsselbloem, say the process may take months rather than weeks.

The reform package includes some fiscal measures and, most importantly, a pension reform, which euro zone officials have described as ambitious in outline, but still lacking numerical details needed for full assessment.

Once the reforms are approved, Greece could get 5.5 billion euros ($6 billion) in the next tranche of loans, Regling told a news conference after euro zone ministers met, but he cautioned that the final amount may be different.

"This will depend on the growth and revenue developments. It does not have to stay that amount," Regling said.

($1 = 0.9208 euros)

(Reporting By Jan Strupczewski; Editing by Ruth Pitchford)