That's a good initiative. If we want to put an end to the shelling which threatens civilians, we must create a buffer zone in the airspace to avert new attacks, he told reporters in Zagreb.
Borrell said that was his, not the official position of the EU, which has yet to discuss a no-fly zone.
Croatian Defence Minister Damir Krsticevic too believes it is necessary to urgently stop the killing of civilians.
It's essential to stop the violence, the war, and then a political solution should be sought. The EU is engaged and this is being worked on, he said.
The situation in northern Syria has deteriorated because of a Syrian army offensive in Idlib province, the last rebel stronghold from which another million people have escaped because of the offensive.
Since last weekend's opening of the border, thousands of migrants have rushed to the Turkish-Greek border in the hope that they will enter Greece, which guards the EU's external border.
European defence ministers discussed the Syrian crisis at an informal meeting in Zagreb. Croatia is currently chairing the EU. The two-day meeting was attended by Borrell, and NATO Secretary-General Jens Stoltenberg on Wednesday.
Europe needs common strategic culture
Borrell said the EU could not impose a no-fly zone alone but that member states could exert influence through other international organisations.
Many member states are in NATO, the UN Security Council. The EU cannot decide on a buffer zone independently, but we can exert influence in places where decisions are made, he added.
Borrell said the crisis in the eastern Mediterranean was an opportunity for Europe to start acting together, more strongly and more independently of transatlantic allies.
We need a common strategic culture. We must understand that there is a certain indivisibility of threats, whether they come from the east or the south, he added.
Krsticevic too is in favour of coordinated EU-NATO action but thinks the EU must be faster in responding to global crises.
The EU has many tools to act and if it wants to be a global actor, we must be faster and more flexible, he said.
Borrell said Europe's ambition to be a global player must be reflected in the EU's 2021-27 budget, currently the subject of tough negotiations between the member states.
We should have resources in line with our ambitions. We can't say that we want a common defence policy and be present in the world if we don't have the money to develop our own capacities, he said.
The positions of European governments differ on many foreign policy issues, from Venezuela and Libya to which stand to take on President Donald Trump's America First policy. They are also divided on the US plan for the Middle East and could not agree for a long time on a maritime mission to enforce an arms embargo on Libya.
Operation Sophia to become history, new mission in the Mediterranean in April
However, Borrell said the new mission should begin in April, replacing Operation Sophia against people smugglers which ends in March.
If people are found at sea, that too should be dealt with, but the new operation will primarily focus on the arms embargo, he added.
In Operation Sophia, more than 500 people smuggling boats were destroyed, 151 suspects were arrested and brought to justice, and 41,000 people were rescued at sea.
That's one of the examples which shows how important it is to manage such operations in which we Europeans use our capacities, said Borrell.
Operation Sophia was launched in 2015 to prevent people smuggling and enforce a UN arms embargo.