US Middle East peace envoy George Mitchell has announced plans to resign, throwing a new question mark over the Obama administration's failed effort to restart direct talks between Israel and the Palestinians.

US officials said Mitchell's resignation would be declared by the White House.

Mitchell's departure comes just days ahead of a May 20 visit to the White House by Israeli Prime Minister Benjamin Netanyahu and an expected speech by President Barack Obama laying out his new Middle East strategy as political turmoil upends decades of US policy in the region.

But Obama is not expected to offer fresh ideas to tackle the Israeli-Palestinian dispute. And Mitchell, 77, had become a symbol of his administration's frustrated ambitions in that arena.

A former US senator who helped broker the Northern Ireland peace deal, Mitchell was one of the first members of Obama's foreign policy team to be named. He shuttled between Washington and Middle East capitals in an unsuccessful bid to launch new negotiations.

There were glimmers of hope. Obama himself presided over the resumption of direct peace talks in September, but the negotiations broke down within weeks over Jewish settlement construction on occupied land in the West Bank.

Faced with a deadlock, the US in December scrapped efforts to relaunch direct peace talks. Mitchell has not visited the region since then.

Obama has recently made changes to his Middle East policy team and nominated Daniel Shapiro, a senior adviser who has helped shape the response to the Middle East upheaval, to be the new US ambassador to Israel.

Mitchell was known as a consummate diplomat, and frequently cited the arduous Northern Ireland peace talks as proof that perseverance is essential when seeking to bridge deep historical divides.

'I don't underestimate the difficulty of this assignment,' Mitchell said when his appointment was announced on January 22, 2009, two days after Obama took office.

'Conflicts are created, conducted, and sustained by human beings. They can be ended by human beings,' Mitchell said. 'I believe deeply that with committed, persevering, and patient diplomacy, it can happen in the Middle East.' – Reuters