He has held an extra unscheduled meeting with Israeli PM Benjamin Netanyahu, with another due on Friday.
The US is seeking a moratorium on settlement building that would be acceptable to the Palestinian side.
It hopes to re-launch peace talks with a Israeli-Palestinian-US summit at the UN General Assembly later this month.
Bilateral talks have been suspended since December and Mr Mitchell has spoken of his "sense of urgency" to get them resume them.
'Positive conclusion'
After meeting Palestinian leader Mahmoud Abbas in Ramallah on Tuesday, following earlier talks with Mr Netanyahu in Jerusalem, Mr Mitchell urged each side to take "concrete steps" to encourage peace.
"We hope to bring this phase of our efforts to a positive conclusion in the coming weeks," he said.
Correspondents say the US has taken an uncharacteristically tough stance against construction by Israel in the West Bank and East Jerusalem, which it occupied in the 1967 war.
The Palestinian leadership says all the land captured in 1967, which also includes the Gaza Strip, must be part of a future Palestinian state, and ultimately seeks the dismantling of all settlements.
In the meantime, Mr Abbas - with US backing - has been demanding a complete freeze on Israeli construction activity.
Mr Netanyahu has offered a temporary freeze for several months, but not in East Jerusalem or in cases where homes have already been approved.
There was no statement after the Wednesday's meeting.
Goldstone controversy
Aside from pressure on freezing settlement, Israel is reported to be looking to Washington - its main ally - to help deflect the impact of Tuesday's UN report on its conduct in the December-January Gaza conflict.
Both the Israeli army and Palestinian militants committed war crimes, and possibly crimes against humanity, according the Judge Richard Goldstone's findings for the UN Human Rights Council.
Israeli media said the biggest threat was seen as the possibility of charges being brought against senior Israeli officials at the International Criminal Court.
Israeli Foreign Ministry officials were said to be contacting all five veto-wielding members of the UN Security Council - including the US - to prevent that from happening.
The Israeli operations, the report found, "were carefully planned... as a deliberately disproportionate attack designed to punish, humiliate and terrorise a civilian population" and amounted to "war crimes, and possibly crimes against humanity"
Israel, which had refused to co-operate with the UN fact-finding team, said the report was "clearly one-sided".
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