"In Europe there is a lot of talk on Nabucco ... but in reality little gets done," Nazarbayev said at a joint news briefing with German Chancellor Angela Merkel in the Kazakh capital, adding that his comments were not criticism.
Kazakhstan remains close to Russia nearly two decades after the breakup of the Soviet Union, but energy has become a bone of contention. Its willingness to join Nabucco could hamper its relations with Russia, Europe's biggest gas supplier.
Nabucco shareholders have struggled to reach the gas supply deals they need to secure financing for around 70% of project costs for the 7.9 billion-euro ($10.25 billion), 3,300-km (2,000-mile) pipeline, Reuters reported.
Nazarbayev added that for Kazakhstan to supply the pipeline, expected to open by end-2014, the Nabucco consortium would have to either extend the link under the Caspian Sea or set up liquefied natural gas plants.
"But nothing is happening with either of those issues besides talk," he said.
Kazakhstan, Turkmenistan, Azerbaijan and Iran are all viewed as potential suppliers for the pipeline, which is expected to carry 31 billion cubic metres a year.
Merkel, who was at the end of a five-day tour to Russia, China and Kazakhstan in the aim of boosting trade and energy supplies, said she welcomed trade with Astana.
"We'll support new business with state export guarantees," she said, referring to Germany's promise to refund exporting companies if the importing country dodges the bill.
Nazarbayev said he was disappointed so few German companies had invested in Kazakhstan and said he would welcome their involvement in the metals and chemicals sectors.
Nabucco's consortium includes Germany's RWE, Austria's OMV, Hungary's MOL, Bulgarian EnergyHolding, Romania's Transgaz and Botas of Turkey.