"The text now needs to be taken into the wider context," European Commission spokeswoman Natasha Bertaud told journalists.
She noted that "at this stage we're not talking about a European Union system" for sharing migrants -- a touchy issue the commission had tried to bring in four years ago but which ran up against fierce opposition from some eastern countries in the bloc.
The details of the four-nation agreement reached in Malta have not been divulged.
They are to be presented at a meeting of all EU justice and interior ministers on October 7 and 8, where further fine-tuning is expected.
Bertaud said the text holds the "contours of a future accord between more member states" and that, while the commission was not in charge of the process, it stood ready to give operational and financial assistance.
The pact is meant to determine which countries would take in migrants arriving in Europe -- usually Italy or Malta -- via the Mediterranean.
The path to the nascent deal was opened by a new Italian government that excludes former interior minister Matteo Salvini, who took a ferocious hardline against migrants.
With him gone, France and Italy were free to argue for a system under which some EU countries could voluntarily take in migrants -- and those that did not would be financially penalised.
France and Germany are reportedly willing to receive 25 percent of people plucked from the Mediterranean.
- Reluctant states -
That penalties provision could prove a difficult pill to swallow for some EU countries reluctant to welcome migrants -- such as the Czech Republic, Hungary, Poland and Slovakia -- making for a contentious ministers' meeting in October.
But the fact that European migration commissioner Dimitris Avramopoulos took part in the four-nation meeting in Malta suggests the EU is throwing its weight behind the pact.
The European bloc in 2016 reached a deal with non-member Turkey to stem the flow of migrants crossing into Greece, dramatically cutting the number of arrivals.
Turkish President Recep Tayyip Erdogan this month warned he could start allowing Syrian refugees to once again travel to Europe if his country did not receive more money under the deal.
According to the EU, more than 90 percent of the six billion euros ($6.6 billion) earmarked to be spent in Turkey has been "allocated", though the amount actually disbursed so far was lower.