The US has issued a worldwide travel alert to its citizens, citing terrorist threats from Isis, al-Qaeda, Boko Haram and "other terrorist groups".
The alert from the US State Department urges US citizens to exercise caution in public places and during holidays and public events.
French President Francois Hollande will meet Barack Obama at the White House on Tuesday to discuss the fight against so-called Islamic State.
The French President has said France is at war with terrorism and that he wants to build a "large coalition" to fight the Islamic State group, which claimed responsibility for the Paris attacks that left 129 people dead.
Speaking after a seven-hour siege that saw security forces raid an apartment in St Denis in search of those behind the attacks, Francois Holland warned that Islamic State threatened the whole world, saying "we are at war".
In a televised address Mr Hollande expressed his gratitude to the security forces who took part in the raid and said he admired the calm of the St Denis residents amid the operation.
France and the US have agreed to step up airstrikes in Syria and Iraq to target IS in the wake of the Paris attacks.
Britain will do "all in our power" to support France in the fight against IS following the Paris terror attacks, David Cameron said.
The United Nations Security Council agreeS to intensify efforts to 'eradicate' Islamic State in the wake of the Paris terror attacks.