BERLIN (Reuters) - Turkey cannot join the European Union if it reinstates the death penalty, German Chancellor Angela Merkel told Turkish President Tayyip Erdogan in a telephone call on Monday, a German spokeswoman said.

Turkish demonstrators rally against the coup attempt in Turkey at the White House in Washington, U.S., July 17, 2016. REUTERS/Joshua Roberts

Turkey abolished capital punishment in 2004, allowing it to open EU accession talks the following year, but the negotiations have made scant progress since then.

With pro-government protesters demanding that the coup leaders be executed, Erdogan said on Sunday there could be no delay in using capital punishment and the government would discuss it with opposition parties.

Merkel told Erdogan on the phone that the European Union and Germany vehemently oppose the reinstatement of the death penalty and that such a step is “in no way compatible” with Ankara’s goal of EU membership, a Berlin government spokeswoman said.

“The chancellor also urged the president to abide by the principles of proportionality and rule of law in the Turkish state’s response (to the coup attempt),” she added. “The recent wave of arrests and dismissals in Turkey are a matter for grave concern.”

Merkel’s comments were echoed by Foreign Minster Frank-Walter Steinmeier, who told reporters in Brussels that Germany expected Turkey to deal with those responsible for the attempted coup in line with the rule of law.

“Reintroduction of the death penalty would prevent successful negotiations to join the EU,” Steinmeier said.

Merkel’s spokesman Steffen Seibert told a news conference earlier on Monday that Germany and the EU categorically reject the death penalty.

“A country that has the death penalty can’t be a member of the European Union and the introduction of the death penalty in Turkey would therefore mean the end of accession negotiations,” Seibert said.

Even before the coup attempt, many EU states were not eager to see such a large, mostly Muslim country as a member, and were concerned that Ankara’s record on basic freedoms had gone into reverse in recent years.

Turkey widened the crackdown on suspected supporters of the coup on Sunday, taking the number of people rounded up in the armed forces and judiciary to 6,000.

German officials said they had seen no evidence of any conspiracy in the events beyond an effort by parts of the Turkish military to seize control of the government.

Erdogan and the Turkish government have accused the U.S.-based Muslim cleric Fethullah Gulen, a former ally of Erdogan, of orchestrating the coup.