The Prime Minister Dr Manmohan Singh on Wednesday said the country will not rest till the perpetrators of the Mumbai carnage are brought to justice. He said, the attack on Mumbai was a calculated attempt by forces outside the country to destabilise India's secular politics and create communal discord. Addressing a press conference in Washington, which is now on, he said this is the solemn duty. He said, the country expects that the master minds of the attack and their supporters should be tried and punished, and the matter has been taken with the government of Pakistan. Dr. Singh said, India has taken several measures to strengthen the security and intelligence system in the wake of Mumbai attacks. He said strengthening the internal security is the top priority of the government. Referring to his visit and discussions with President Obama, Prime minister said both the countries can work together to accelerate global economic recovery.