* Socialist president tells parliament "France is at war"
* Will meet Obama, Putin to seek single coalition in Syria
* Islamic State is enemy but Assad can't be solution -Hollande (Adds centre-right opposition rejects changing constitution)
By Emile Picy
VERSAILLES, France, Nov 16 (Reuters) - French President Francois Hollande appealed on Monday for a grand coalition including the United States and Russia to eradicate Islamic State in Syria after bloody militant attacks on Paris.
In a solemn address to a joint session of parliament in the Palace of Versailles that began with the words "France is at war", Hollande announced an increase in police recruitment, a halt to layoffs in the army and a constitutional amendment to strengthen the fight against "war by terrorism".
Friday's attacks by gunmen and suicide bombers at restaurants, bars, a soccer stadium and a music hall that killed 129 people and wounded more than 350 were ordered from Syria, planned and prepared in Belgium and carried out with the help of French citizens, he said.
Hollande said he would meet U.S. President Barack Obama in Washington and Russian President Vladimir Putin in Moscow in the coming days "so we can unite our forces to achieve a result that has taken too long".
A U.S.-led coalition has been bombing Islamic State for more than a year. Russia joined the Syria conflict in September, but U.S. officials say it has mainly hit foreign-backed rebels battling its ally President Bashar al-Assad, not Islamic State.
Hollande said that while Assad could not be part of the solution to the crisis, "our enemy is Daesh (Islamic State)". He insisted that France was fighting terrorism and not another civilisation.
"We will eradicate terrorism," Hollande declared at the end of a 50-minute speech. Lawmakers from all parties gave him a standing ovation and sang the "Marseillaise" national anthem.
The Socialist president said he had ordered air strikes on headquarters of Islamic State in the Syrian town of Raqqa overnight and would continue to wage war "mercilessly", sending an aircraft carrier to triple French air power in the region.
He also said France wanted more effective controls of the European Union's external borders to avoid a return to national border controls and the dismantling of the 28-nation EU.
Additional security spending would be needed and France would not let EU budget rules to get in the way, Hollande said.
He said he would invoke a mutual defence clause in the EU's Lisbon treaty, which requires member states to give each other assistance if they come under attack. Hollande made no mention of the U.S.-led NATO military alliance's mutual defence clause.
He said security forces had put more than 100 people under house arrest and raided 168 premises since he declared a state of emergency, which he asked parliament to extend for three months.
He also proposed measures to speed up the expulsion of foreigners considered a threat to public order, strip dual nationals who carry out acts hostile to national security of French citizenship, and bar dual nationals considered a terrorism risk from entering French territory.
Speaking for the main centre-right opposition, Republicans floor leader Christian Jacob said he could see no justification for amending the constitution, which he said was unnecessary.
"Our constitution clearly provides the legal tools to cope with any situation," Jacob told lawmakers after Hollande had left the chamber. A constitutional amendment requires a three-fifths majority of the Congress of both houses or a referendum vote.
It was the first time in more than six years that a president had addressed both houses of parliament convened in a so-called Congress at Versailles, a procedure reserved for constitutional revisions and major presidential speeches.
Former conservative President Nicolas Sarkozy last addressed the Congress at the former royal palace in 2009, at the height of the global financial and banking crisis.
The Congress took place in the spectacular Southern Wing of the former royal palace built by Louis XIV, in an ornate chamber decorated with allegorical paintings evoking war and peace. (Additional reporting by Ingrid Melander and Michel Rose; Writing by Paul Taylor; Editing by Mark Heinrich)