The present invention relates to a process for preparing difluoromethyl-substituted pyrazol-4-ylcarboxylic acids and their esters, 2-(aminomethylidene)-4,4-difluoro-3-oxobutteric esters of the formula (I) in which R1, R2 and R3 independently of one another are C1-C6-alkyl, C1-C6-haloalkyl, C2-C6-alkenyl, C3-C10-cycloalkyl or benzyl or NR2R3 is a 5- to 10-membered heterocyclic radical, to a process for preparing compounds of the formula (I) wherein an appropriate 3-aminoacrylic ester is reacted with difluoroacetyl fluoride and to the use of compounds of the formula (I) in the process for preparing difluoromethyl-substituted pyrazol-4-ylcarboxylic acids and their esters.