JERUSALEM - The European Union on Monday called Israel's closure of Gaza "unacceptable" and offered to play a role in opening the borders, as Israel appointed three Israeli experts and two foreign observers to a commission to investigate its deadly raid on a Gaza-bound flotilla.

The EU move added to the intense pressure on Israel to lift the blockade since nine pro-Palestinian activists died in clashes after Israeli commandos rappelled aboard one of the aid ships last month.

The three-year closure has withheld all but the most basic supplies from Gaza's 1.5 million Palestinian residents.

The most notable dissent has come from President Obama, who called the Gaza closure unsustainable. The U.S. pressure resonates more with the Israelis because of their close alliance with Washington.

International envoy Tony Blair also called for the blockade to be eased and said there were indications Israel was prepared to consider doing that.

Israel has maintained the blockade to keep weapons and missiles out of the hands of the Islamic Hamas, which has ruled Gaza since 2007; to undermine support for Hamas among Gazans; and to press for release of Gilad Shalit, an Israeli soldier held in Gaza for four years.

None of those goals has been achieved, but Israel warns that lifting the embargo altogether would allow Hamas, which does not recognize Israel's right to exist, to bring in unlimited weapons and missiles to be turned against the Jewish state.

The 27-nation EU has consistently opposed the blockade, citing the hardships it causes to Gazans.

In Luxembourg on Monday, the EU called the blockade "unacceptable and politically counterproductive," saying it was prepared to return to an active role in helping supervise Gaza's border crossings.

The EU helped run the Egypt-Gaza crossing before Hamas overran the territory in 2007 and the EU observers were withdrawn.

The EU, like the United States and Israel, considers Hamas a terrorist group and does not have direct contacts with Gaza's rulers. The statement said the EU would continue contacts with Israel, the Palestinian Authority of President Mahmoud Abbas - whose forces were expelled from Gaza by Hamas - and "other appropriate parties," without mentioning Hamas.

Despite that, Hamas has felt vindicated by the outcry over the bloody flotilla attack.

Several ideas are being floated to improve the dire situation in Gaza, where people have adequate basic food but little else - no exports, few consumer products, no raw materials, and few construction supplies to rebuild damage from the Israel-Hamas war 18 months ago.

The main thrust of the EU statement was a demand to open the borders to civilian goods, with strict safeguards.

"To this end, full and regular access via land crossings, and possibly by sea, on the basis of a list of prohibited goods, should be the prime aim," the statement said.

Israel has maintained a list of items it permits into Gaza through its crossings, banning the rest. Replacing that with a list of forbidden items, like weapons, and letting everything else in is among the ideas on the table, said an Israeli official who spoke on condition of anonymity.

While considering ways to ease pressure over the blockade, Israel also sought Monday to blunt calls for an international investigation of the May 31 flotilla attack.

Israel named its own inquiry commission, headed by retired Israeli Supreme Court Justice Yaakov Turkel, joined by 93-year-old legal expert Shabtai Rosen and Amos Horev, a retired general and former president of the Technion, an Israeli university.

Israel's cabinet also approved two prominent international observers: David Trimble, a Nobel peace laureate from Northern Ireland, and Canada's former chief military prosecutor, retired Brig. Gen. Ken Watkin. Trimble, a member of the British House of Lords, belongs to a pro-Israel faction in Parliament.

Abbas rejected the commission, asserting it falls short of U.N. Security Council demands for an "impartial" investigation. A U.N. spokesman said Secretary-General Ban Ki-moon still wanted an international inquiry.