bbc: german chancellor angela merkel has promised a new push to send home failed asylum seekers after berlin truck attacker anis amri murdered 12 people. she caled for a "national effort" to ensure that anyone who had a right to protection was integrated while those denied it should leave. germany turned down amri's asylum bid in june but failed to deport him because tunisia refused to accept him. ministers are preparing tougher rules for such cases in future. the chancellor said the attack showed that the government had to "act faster, act correctly, not just to get stuck with announcements but also to show where it really stands". justice minister heiko maas believes the authorities should have the right to detain for an 18-month period individuals who are designated a threat to security and given a deportation order. more than 220 foreign suspects in germany have reportedly been labeled as potential threats. 'electronic tags not a taboo' anis amri was not kept in custody because he did not have tunisian documents. although he was seen as a security risk by authorities in the western state of north rhine-westphalia for planning a serious act of violense , he moved to berlin and was not detained because of a lack of evidense . the justice minister said such suspects should be made to wear electronic tags even without a conviction. "electronic ankle monitors should not be a taboo," maas said. although they were not a complete solution, they could help improve monitoring of suspects, he argued. he is due to meet interior minister thomas de maiziere on tuesday to seek agreement on security measures. de maiziere has already caled for special centres to be set up to house rejected asylum seekers. however, part of the problem for the german government has been its difficulty in sending people back to tunisia, algeria and morocco. the chancellor said reaching an agreement with such states would only succeed if respect was shown to them. "those who have no residency status must be returned to their homeland, but that also demands of us that we concern ourselves with the problems of these countries and find solutions that are in our mutual interest," merkel said on monday. the opposition green party has so far refused to back a move to declare the three countries as "safe countries" for deporting failed asylum seekers. the head of the left party, bernd riexinger, warned that anyone "frantically" caling for stricter punishments was slowly caling into question germany's rule of law.