In an article published on the Politico website Saturday, Erdogan said European leaders "ought to talk a little less and focus on taking concrete steps" in the conflict-torn North African nation.
Erdogan will join leaders from Russia, the West and Arab countries, as well as the heads of the opposing Libyan factions, in the German capital on Sunday in a bid to halt nine months of fighting around the Libyan capital of Tripoli.
A truce sponsored by Turkey and Russia was imposed a week ago, although there have been reports of continued fighting.
Turkey supports the U.N.-backed administration in Tripoli led by Fayez Sarraj and sent troops to Libya earlier this month to help them in their battle with eastern-based forces led by Gen. Khalifa Hifter.
In the article, Erdogan labeled Hifter a "warlord" and "coup plotter." He said a failure to support Sarraj would be a betrayal of the E.U.'s values and a mistake of "historic proportions."
If the Tripoli government were to fall, Libya would become a "fertile ground" for the re-emergence of extremists like the Islamic State group and al-Qaida, Erdogan said. Further instability would also fuel more migration from Libya towards Europe across the Mediterranean Sea.
"The Libyan civil war serves as a litmus test for the E.U.," he said. "Will European leaders uphold the liberal world order in the face of yet another attack? Or will they abdicate their responsibilities, as they did in Syria, to watch the crisis unfold from the sidelines?"
Germany is bringing together key players in Libya's long-running conflict in a bid to curb foreign military meddling, solidify the cease-fire and help relaunch a political process to determine Libya's future.
Serraj's government is backed by Turkey, Qatar and Italy while Hifter is supported by Egypt, the United Arab Emirates, Saudi Arabia and France. Russian military contractors have been fighting alongside Hifter's forces, although Moscow retains links to both sides in the conflict.
In November, Turkey and the Libyan government in Tripoli signed a controversial maritime deal on delineating a boundary between the two countries in the Mediterranean. The agreement would give Turkey and Libya access to an economic zone despite the objections of Greece, Egypt and Cyprus, which lie between the two geographically.
Erdogan called on Europe to work with Turkey as it trains Libyan forces to combat terrorism, human trafficking and other threats to international security.
"Europe finds itself at a crossroads," he said. "And at this historic junction, those working for peace must be courageous and do everything in their power to end violence.
"Europe can count on Turkey — an old friend and ally — to achieve that goal."