UNITED NATIONS — A drama on the high seas is brewing in the Mediterranean as a Turkish government-backed flotilla, laden with various goods and carrying hundreds of pro-Palestinian activists, is attempting to reach Gaza’s shores in the next few days to deliver what its members say is much needed humanitarian aid to the Hamas-controlled strip.

Israel’s Navy said it would prevent the flotilla from entering Gaza and, if necessary, board the eight boats and arrest the activists. Nevertheless, government spokesmen say the cargo, estimated at $20 million worth of material, would then be delivered to Gaza from Israel, but only after undergoing inspection to assure it includes no terror-related items.

The drama, which is expected to further heighten the already tense relations between Ankara and Jerusalem, will peak Friday, when the boats, loaded with 800 activists, mostly from Turkey, Europe, and Israel, will set sail from Cyprus toward Gaza. Earlier today, military spokesmen publicly detailed plans to bar their entry into Israeli controlled waters.

Activists, including a handful of Americans, have been just as adamant that they will not obey the Navy’s orders to turn around. They vowed to “break the blockade” that Israel has imposed on Gaza since 2007, when it was taken over by Hamas in a bloody coup that ended the brief rule of the Palestinian Authority after Israel evacuated the strip a year earlier.

The United Nations, which has the largest foreign presence in the strip, has long urged Israel to allow more goods into Gaza. U.N officials at Gaza have expressed support for the flotilla. Nevertheless, the U.N. itself has “no plans to use sea routes onto Gaza, but will consider all legal options available” to allow as many goods as possible to be brought in, U.N. spokesman, Martin Nesirky, told me yesterday.

The legality of transferring goods into Gaza is murky, as it is governed by agreements made in 2006 between Israel and the Palestinian Authority. Those pacts were declared null and void once the PA relinquished the strip to Hamas, which is yet to recognize any agreement with Israel.

Although participants of the so-called “aid flotilla” have widely been described as NGO members, they have been backed by the Turkish government. Prime Minister Erdogan has urged Israel to allow the cargo into Gaza.

Israel’s Defense Minister, Ehud Barak, has issued a closure order for the next few days, covering 20 miles around Gaza’s shores. The navy plans to use all lines of communication to inform the organizers of the closure. If, as expected, the ships refuse to turn back, navy forces, including troops from the elite unit Shayetet 13, will board the ships, arrest the 800 activists, and take them to the port of Ashdod, where they’ll be issued deportation orders.

Last week, the foreign ministry deputy director general for Western Europe, Naor Gilon, called into his Jerusalem office the ambassadors of Turkey, Greece, Ireland, and Sweden, whose citizens participate in the flotilla, informing them of the government’s decision to block entrance. Mr. Gilon also told the ambassadors that the planned trip was no more than a provocation and a “blatant violation of Israeli law.”

Israeli officials say there is no humanitarian crisis in Gaza, and U.N. officials acknowledged that goods related to local projects were allowed in. Secretary General Ban recently denounced an assault by Arab militants on camps the U.N. organizes on Gaza’s shores every year for Palestinian children. Saying that the camps are a Western plot to undermine Islam, masked men set fire to two of the camps.

In contrast to that incident, which received little Western attention, the clash expected Friday between navy and activists could become a well-televised public relations nightmare for Israel. The government has tried to stem criticism in advance, publicly detailing the quantities of goods Israel has allowed into Gaza, even during direct cross-border attacks by Hamas-backs militants.

Mr. Erdogan has turned his back on the decades-long warm relations between Turkey and Israel. His anti-Israel demarche started in January 2009, when he launched a verbal assault against President Peres at a Davos forum. Since then, Mr. Erdogan has often stressed the purported suffering in Gaza, even as he tightened Turkey’s relations with Hamas-backing Iran.

Mr. Ban, who visited Turkey last week, praised Mr. Erdogan’s attempts at mediating between Israel and Syria. But the government of Prime Minister Netanyahu has long said that it no longer sees any mediating role for Mr. Erdogan, at least as long as his anti-Israeli rhetoric continues to escalate.