Israel's Supreme Court on Tuesday reduced former Prime Minister Ehud Olmert's prison sentence for a sweeping bribery scandal from six years to 18 months, partially accepting his appeal and clearing the ex-premier of the main bribery charge against him.

The court announced Olmert will begin serving his sentence on Feb. 15 — the first Israeli leader to ever serve behind bars. Though the ruling marked a legal victory for Olmert's team, the top court upheld part of his conviction for taking a lesser bribe.

Olmert, 70, was convicted in March 2014 and sentenced to six years in a wide-ranging case that accused him of accepting bribes to promote a controversial real-estate project in Jerusalem. He was charged for acts that happened while he was mayor of Jerusalem and the country's trade minister, years before he became prime minister in 2006.

Olmert has denied any wrongdoing and was allowed to stay out of prison until the verdict on his appeal was delivered.

After Tuesday's verdict was handed down, Olmert said he was "satisfied" about his partial exoneration. He added it was still a "hard day" but he said he accepted the Supreme Court's ruling.

"A stone has been lifted from my heart," he said. "I said in the past, I was never offered and I never took a bribe. And I say that again today."

The ruling marks a dramatic climax for a man who only years earlier led the country and hoped to bring about a historic peace agreement with the Palestinians.

Olmert was forced to resign in early 2009 amid the corruption allegations. His departure cleared the way for the election of hard-liner Benjamin Netanyahu, and subsequent Mideast peace efforts have failed.

Olmert was a longtime fixture in Israel's hard-line right wing when he began taking a more moderate line toward the Palestinians when he was deputy prime minister a decade ago. He played a leading role in Israel's withdrawal from the Gaza Strip in 2005.

He became prime minister in January 2006 after then-Prime Minister Ariel Sharon suffered a debilitating stroke. He subsequently led their newly formed Kadima Party to victory in parliamentary elections on a platform of pushing further peace moves with the Palestinians.

Appeal pending in separate case

A gifted orator, Olmert crossed a series of taboos while in office — warning that Israel could become like apartheid South Africa if it continued its occupation of the Palestinians and expressing readiness to relinquish control of parts of the holy city of Jerusalem as part of a peace deal.

He led his government to the Annapolis peace conference in November 2007 — launching more than a year of ambitious, but unsuccessful peace talks with the Palestinians. Olmert enjoyed a warm relationship with then President George W. Bush.

Olmert has said he made unprecedented concessions to the Palestinians during those talks and was close to reaching an agreement at the time of his resignation, though the Palestinians have said his assessment was overly optimistic.

Despite his ambitious agenda, Olmert's term was clouded by the kidnapping of an Israeli soldier who was captured by Gaza militants in a cross-border raid and an inconclusive war against Hezbollah guerrillas in Lebanon. Both incidents occurred shortly after he took office. Olmert also launched a military invasion of the Gaza Strip in late 2008 that drew heavy international criticism.

But it was corruption allegations, which had dogged him throughout his career, which ultimately proved his undoing. He was forced to announce his resignation in late 2008 and left office early the following year.

In a separate case, Olmert was sentenced earlier this year to eight months in prison for unlawfully accepting money from a U.S. supporter. He is also appealing that sentence.