Updated at 1.45pm
Brexit has made EU states more determined and united, the European Council president said, as he warned against the threat of populism in Europe.
EU leaders present in Malta this morning are calling for unity across Europe as the union goes through testing times.
Speaking at the European People's Party congress, Donald Tusk said the key to the future is in the unity and sovereignty of Europe.
He warned against "foolish and dangerous claims" made under the guise of sovereignty and patriotism.
"We must challenge the populists, we must say loud and clear that nationalism and separatism which threatens the EU is the opposite of patriotism. Words such as 'dignity' and 'pride' must return to our political dictionary," he told those present at the Intercontinental Malta.
We must challenge the populists, we must say loud and clear that nationalism and separatism which threatens the EU is the opposite of patriotism
He said populists are taking advantage of organised hatred and the EU's response must be clear and decisive. Only free and law-abiding societies can truly be safe.
Hosted by the Nationalist Party, the EPP congress is taking place just hours after the UK triggered off Article 50, paving the way for Britain's exit from the European Union.
Antonio Lopez-Istruiz, general secretary of the EPP, said the EU was united and strong "to face whatever letters are sent from London or to respond whatever tweets president Trump might direct to us".
"We are strong and united but we muse listen and reconnect with those who voted for socialists. Extremists and populists will not succeed," he said.
Outlining a number of struggles, including Brexit, the economic crisis, terrorism attacks and the refugee crisis, ministers and heads of states reiterated calls for unity and peace among all states.
European Commission president Jean-Claude Juncker said Brexit is not the end of the EU.
"US president Donald Trump was happy that Brexit took place and he is asking other countries to do that. If he continues, I will suggest that Ohio and Texas are independent."
Populism is biggest challenge - Busuttil
Nationalist Party leader Simon Busuttil said populism was the biggest challenge faced by the EU.
"The populist promises everything to everybody, the populist speaks about problems but never offers solutions. Populists are just interested in votes."
This was evident after the Brexit vote when the ones campaigning for Britain's exit from the EU came up with no alternatives.
Concluding the congress, Dr Busuttil said: "I will do my best to deliver the next EPP government, and to deliver the govenrment that the people of Malta truly deserve - and we will leave no stone unturned to get this job done."
Donald Tusk. Photo: ReutersEPP group chairman Manfred Weber said if the EU wanted to convince people of its unity it must stop the everyday crisis talks which have dominated its agenda.
"Every political era had challenges. We can solve the problems better together. I am 44 and I am the first generation to say I have lived in a peaceful Europe and so do not tell me that this is not a success story."
He described statements made by Turkish leader Erdogan as unacceptable.
"Turkey cannot become a member of the EU. We should have a partnership but not membership. Do not overstretch the EU," he told those present.
As Britain prepared to leave the EU, the bloc cannot allow the "cherry-picking approach" it had seen in the past decades.
German chancellor Angela Merkel said if Europe wants to protect its external borders, it also has to tackle the reasons why people are fleeing.
"The truth is we have looked away when we came to funding camps and that is why we are facing humanitarian disaster and that is why we took refugees in.
"When you fly to Malta and see the blue skies… you see that Africa is on their doorstep. We have to help African states take their fates into their own hands," she said.
Spanish Prime Minister Mariano Rajoy said Europe has to emerge stronger from the economic crisis.
"We are the major commercial power in the world. We are the place in the world where people are given best care. Nobody has education and health systems as we do and that is why everyone wants to come to Europe."
Silvio Berlusconi entering the EPP congress in St Julian's.In the wake of Brexit, Hungarian Prime Minister Victor Orban called for negotiations that were fair and which reflected the EU’s values while Romania Prime Minister Krause Iohannis called for negotiations that were “sustainable”.
“It is extremely important that the outcome of negotiations have to have results which are decent and sustainable. The main policies can be towards what can unite us. Avoid more dividing lines.
“Romania does not support EU of concentric circles and multiple speeds. It risks division. We do not see this as depending cooperation especially when the union is already rife with distrusts,” Mr Iohannis said.
European People’s Party President Joseph Daul called for openness and tolerance towards other cultures across Europe.
He told the congress, being held ahead of a vote on a resolution on countering Islamic extremism, that Muslims born in Europe had for years formed an integral part of society and this needed to be upheld even today.
He did, however, warn against Sharia law being introduced above other laws, saying Europe had to ensure freedom of religion but not against any other rules.