Prime Minister Benjamin Netanyahu on Friday slammed Germany’s foreign minister as “insensitive” for refusing to cancel meetings with rights groups critical of Israel’s government, amid rising tensions between the two allies.

Netanyahu scrapped talks with Sigmar Gabriel at the last minute on Tuesday, after Germany’s top diplomat pressed on with plans to meet with Israeli rights groups Breaking The Silence and B’Tselem.

In an interview with Germany’s biggest selling Bild daily, Netanyahu defended his decision.

“Foreign diplomats are welcome to meet with civil society activists and members of the opposition and anyone else they’d like,” he said.

“But my red line is that I will not meet diplomats who come to Israel and lend legitimacy to fringe radical groups that falsely accuse our soldiers of war crimes and undermine Israeli security,” he added.

Pointing out that the meetings with the activist groups were held a day after Israel was commemorating the victims of the Holocaust, Netanyahu said that “it was a particularly insensitive time to seek a meeting like this.”

“These are the days we mourn the murdered members of our people in the Holocaust and our fallen soldiers. The Israeli army is the one force that keeps our people safe today,” he said.

Netanyahu tried to call Gabriel after canceling the meeting to explain his decision, but the German minister refused to take his call, several Hebrew media outlets reported on Tuesday afternoon.

However, Gabriel told German newspaper Der Spiegel Friday that Netanyahu offered to speak with him on the phone instead of meeting him, but only on two conditions: That Gabriel not attend the meetings with Breaking the Silence and B’Tselem personally, but instead send someone else from his delegation, and that a representative from the settler movement attend those meetings as well.

The Prime Minister’s Office denied this, saying that Netanyahu was prepared to have a phone conversation unconditionally.

Netanyahu’s decision to cancel the meeting with Gabriel was a rare step, but in line with the current right-wing government’s stance against groups it accuses of unfairly tarnishing Israel.

Due to its historical responsibility as the perpetrator of the Holocaust that killed six million Jews, Germany has not only been Israel’s staunch ally but has also been cautious in its public criticism of the Jewish state.

However, tensions have grown as Netanyahu has irked Berlin by pressing on with settlement building in the West Bank despite repeated warnings from world powers that it would harm any prospects for peace.