US Secretary of State John Kerry on Sunday hailed the commitment of the outlawed Kurdistan Workers' Party (PKK) to a ceasefire under a renewed push by the Turkish government to end three decades of hostilities.

"We welcome the PKK's commitment to lay down its arms," Kerry told a news conference in Istanbul with Turkish Foreign Minister Ahmet Davutoglu.

"We discussed our work to combat terrorism in all its forms ... including the violence that has plagued Turkey for three long decades," he said.

"No peace process is easy. It always take courage and determination."

Both countries are members of NATO, and the United States has for several years supported Ankara in its fight against the PKK on Iraqi soil.

The PKK is blacklisted as a terror group by Ankara, the European Union and the United States.

Jailed Kurdish rebel chief Abdullah Ocalan last month called for a ceasefire in a move that raised expectations for an end to a conflict that has cost some 45,000 lives, mostly Kurdish.

In a letter penned from his island prison cell, Ocalan told his fighters to lay down their arms and withdraw from Turkish soil.

The move capped months of clandestine peace talks between Turkey's spy agency and Ocalan, the state's former nemesis, with the ultimate goal of disarming the rebels who use bases in Iraq as a springboard to launch attacks on government security forces in the Kurdish-majority southeast.