Istanbul (AFP) - President Recep Tayyip Erdogan warned the European Union Tuesday it needs Turkey more than Ankara needs the bloc, as tensions grew over promises for visa liberalisation in a crucial deal on stemming the flow of migrants to Europe.

Turkish Prime Minister Ahmet Davutoglu had earlier bluntly told the EU that Ankara would no longer abide by the March migrant accord if Brussels fails to implement the pledge to grant Turks visa-free travel by June.

Tensions have also been fuelled by a European Parliament report published last week that accused Turkey of backsliding on democracy and pressure from Ankara on Berlin to prosecute a German comic over a poem satirising Erdogan.

The issues are coming to a head as Chancellor Angela Merkel and top EU officials prepare to travel Saturday to the Turkish city of Gaziantep close to the Syrian border to discuss implementation of the migrant deal.

"The European Union needs Turkey more than Turkey needs the European Union," Erdogan said to cheers in a televised speech to municipal leaders in Ankara, denouncing as "provocative" the European Parliament report.

He lashed out at the report for not praising Turkey's hosting of some 2.7 million refugees from the war in neighbouring Syria.

"Three million people have been looked after in this country so they don't disturb the Europeans. Is there anything about this in the report?" said Erdogan.

"At a time when our relations with the European Union are in a positive phase regarding the migrants... it is provocative to come out with a report like that."

- 'Mutual commitment' -

Turkey has been given a string of promises from the European Union -- including visa-free travel to the border-free Schengen Zone and new momentum for its long-stalled membership bid -- in return for stepping up efforts to stop migrants crossing to EU territory.

"This is a mutual commitment," Davutoglu said on Monday of the promise to exempt Turks from visas by the end of June.

"If the EU cannot take the necessary steps required of it then of course it cannot be expected of Turkey to take these steps," Davutoglu told reporters before heading to Strasbourg to address the Parliamentary Assembly of the Council of Europe (PACE).

If the June deadline is not adhered to, "of course no-one can expect Turkey to adhere to its commitments," he added.

Marc Pierini, visiting scholar at Carnegie Europe, told AFP that Ankara was "very keen" to obtain the visa-free regime but was also aware there were are 72 technical conditions to be fulfilled.

"As of today, these conditions have not been met yet," he said.

Once they are met, the issue will be put to EU interior ministers for a qualified majority vote in June.

"Turkey does not have the ability to change the voting procedures in EU Ministerial Councils," Pierini commented.

- 'Won't be watered down' -

EU Commission chief Jean-Claude Juncker also warned Ankara on Tuesday that the "criteria (on visa liberalisation) will not be watered down in the case of Turkey".

He said Davutoglu had raised the issue in talks in Strasbourg "but he did not need to because... I have made clear that this will be done when Turkey has fulfilled all the conditions, which it is in the process of doing."

He added: "We concluded an accord and this deal is being applied. There is no need to make any kind of threat."

The March 18 accord sets out measures for reducing Europe's worst migration crisis since World War II, including stepped-up checks by Turkey and the shipping back to Turkish territory of migrants who land on the Greek islands.

But the prospect of visa-free travel for Turks has been hugely controversial in some EU countries, where leaders have been accused of bending over to fulfil Erdogan's demands at a time when he is accused of growing authoritarianism.

In his address to the PACE, Davutoglu did not emphasise the visa issue but lamented the lack of foreign assistance given to Turkey for the Syrian refugees, saying this amounted to just $500 million (440 million euros) compared to Turkey's spending of $10 billion.

He warned of the risk of a "lost generation" with 152,000 Syrian children born in Turkey and 400,000 children who do not have access to eduction.