US President Barack Obama today warned of a “credible terrorist threat” against America after the overseas discovery of two US-bound packages containing explosives aboard cargo jets. Obama said the packages, which according to the officials originated in Yemen, had been addressed to two Jewish centres in Chicago area. However, the White House said the latest terrorist plot would have no impact on Obama's upcoming trip to India and other Asian nations. The US President was briefed by his top intelligence officials and national security aide on the latest terrorist threat to the US. Obama told reporters in a hurriedly-convened White House press conference that the Administration would not spare any efforts in investigating the origins of the suspicious package. He said the packages were identified in Dubai and Britain. Obama announced that there would be additional screening of some planes in Newark and Philadelphia. He said more protective measures would be taken for as long as it takes.