* EU, Iceland talks over mackerel fishing collapse
* EU fish chief considering blocking Icelandic boats
* Iceland slams EU-Norway agreed catch levels
(Adds detail, background)
By Pete Harrison
BRUSSELS, Dec 14 (Reuters) - The EU's fisheries chief is considering blocking Icelandic fishing vessels from landing some catches in European Union ports in a row over mackerel that threatens Iceland's bid to join the bloc, an EU source said.
Iceland, which suffered heavily with the collapse of its banking system, started talks earlier this year on joining the 27-country EU, which it hopes may bring greater stability and financial security.
But the island of 320,000 has also sought to cash in on an explosion of mackerel stocks in its waters, after the fish started swimming further north than usual.
That has brought it into conflict with the traditional mackerel-fishing nations of Scotland, Ireland and Norway, which have until now managed the catch levels between them.
EU fisheries commissioner Maria Damanaki told fisheries ministers meeting in Brussels on Tuesday she was considering invoking laws "which would allow us to refuse landings of mackerel from Icelandic vessels in EU ports", said the source, who was present at the meeting.
Her team are already working on concrete measures to prohibit landings wherever an international dispute erupts, the source added.
The dispute has escalated since fishing talks broke down in the summer and Iceland unilaterally raised its quota to allow its fishermen to catch 130,000 tonnes of mackerel, compared to a traditional catch that the EU estimates at 2,000 tonnes.
Three EU commissioners, including Damanaki and the commissioner in charge of EU enlargement, Stefan Fuele, wrote to Iceland in October warning that failure to find a solution to the "mackerel war" threatened their relations. [ID:nLDE62K04S]
The conflict has prompted comparisons with the "cod wars" of the 1950s and 1970s, which led to a naval stand-off between Iceland and Britain.
Iceland says more than 1 million tonnes of mackerel, a quarter of the stock, migrated into its exclusive economic zone during the five-month summer feeding season. It intends to maintain this year's 17 percent share of the north Atlantic catch in 2011.
It also criticised the EU and Norway on Tuesday for failing to take that into account when they jointly decided this week to take 583,882 tonnes of mackerel in 2011, the majority of the amount that scientists say is ecologically safe to catch.
"If the EU and Norway do not reconsider their decision, they will bear the responsibility of overfishing from the stock next year," Iceland's mackerel negotiator said in a statement. (Editing by Rex Merrifield)
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