Former U.S. lawmaker Cynthia McKinney is due to appear in an Israeli court Sunday after she and 20 other activists were taken into custody this week when their relief boat was seized by an Israeli naval ship.

The 2008 Green Party presidential candidate says the group, "Free Gaza Movement," was trying to deliver humanitarian supplies to Gaza, but Israel says the boat attempted to sail through a navy blockade.

Israel said it would free the crew and passengers as soon as they were checked, but McKinney and the others say they refused to sign deportation forms because it would have entailed admitting they violated Israel's blockade.

"The Israelis hijacked us because we wanted to give crayons to the children of Gaza," McKinney said in a recorded statement delivered via telephone and posted on YouTube.

McKinney and the other activists left Cyprus on Tuesday on a Greek-flagged boat called the Spirit of Humanity, which was carrying medical supplies, cement, olive trees and children's toys en route to Gaza.

The Israeli military issued a statement Tuesday saying the boat had attempted to break a blockade of Gaza and was forced to sail to an Israeli port after ignoring a radio message to stay out of Gaza waters.

Israel officials have since promised to deliver by ground all of the humanitarian supplies that were on the boat.

The group, which has been in custody since Tuesday, will be held at least until Sunday, when the activists are to appear in court.

Two activists -- both Israeli citizens -- have been released, but the others are being held in Givon prison in Ramla, Israel.

The State Department and White House have not publicly responded to McKinney's appeal for help.

"State Department and White House officials have not effected our release or taken a strong public stance to condemn the illegal actions of the Israeli Navy of enforcing a blockade of humanitarian assistance to the Palestinians of Gaza, a blockade that has been condemned by President Obama," she said in a statement.

The office of the Consulate General of Israel in Atlanta said McKinney's release is imminent.

"According to Israeli law, Ms. McKinney and her fellow crew members were suggested to sign a form acknowledging their deportation. Since Ms. McKinney has refused to do so, she is expected to appear before an Israeli judge on Sunday, July 5, and afterwards be returned home as soon as possible," the office said in a statement released Friday.

Leola McKinney, mother of the former congresswoman, told the Atlanta Journal-Constitution that her daughter did not sign the form because it was in Hebrew.

"She didn't know what she was signing," Leola McKinney told the newspaper.

It was the second time in a year that McKinney's relief boat was seized by an Israeli naval ship, but it's the first time that the longtime supporter of Palestinians has been detained. In December, McKinney was among 16 people aboard a medical supply boat that collided with an Israeli naval ship as it tried to enter coastal waters around Gaza.

Israel launched an offensive in December against Gaza in an attempt to halt years of Palestinian rocket attacks on southern Israel. The two sides reached a cease-fire in January.

Click here to read the Atlanta Journal-Constitution report.