By Steve Holland, Simon Lewis and Samia Nakhoul

WASHINGTON, Feb 19 (Reuters) - U.S. President Donald Trump will preside over the first meeting of his Board of Peace on Thursday with unresolved questions on the future of Gaza hanging over an event expected to include representatives from more than 45 nations.

The disarmament of Hamas militants, the size of the reconstruction fund and the flow of humanitarian aid to the war-battered populace of Gaza are among the major questions likely to test the effectiveness of the board in the weeks and months ahead.

Oil prices rose to multi-month highs while global stocks mostly retreated as markets weighed sharpening rhetoric from President Donald Trump on Iran suggesting a military strike was more likely.

Brent oil futures finished up nearly two percent at $71.66 a barrel after earlier reaching its highest level since July.

"Oil is extending its gains, with Brent crude back above $70 a barrel... as fears of a military confrontation between the US and Iran rattled energy markets," said Matt Britzman, senior equity analyst at Hargreaves Lansdown.

Feb 18 (Reuters) - Russian Foreign Minister Sergei Lavrov, in an interview made public on Wednesday, said that any new U.S. strike on Iran would have serious consequences and called for restraint to find a solution to enable Iran to pursue a peaceful nuclear programme.

Lavrov's interview with Saudi Arabia's Al-Arabiya television was aired a day after U.S. and Iranian negotiators held indirect talks in Geneva to head off a new mounting crisis between Washington and Tehran.

US President Donald Trump on Thursday promised $10 billion and Muslim-majority nations offered funding and troops for Gaza as he inaugurated his "Board of Peace," a new institution whose ultimate mission has drawn questions.

Trump brought together allies from around the world -- many authoritarians, with few Western democrats who traditionally ally with the United States -- to hail his peacemaking just as he sends US military might near Iran and threatens war.

WASHINGTON, Feb 18 (Reuters) - Iran is expected to submit a written proposal on how to avoid its standoff with the United States in the wake of U.S.-Iran talks in Geneva on Tuesday, a senior U.S. official told Reuters on Wednesday.

Top national security advisers met in the White House Situation Room to discuss Iran and were told all U.S. forces deployed to the region should be in place by mid-March, the official said.

Secretary of State Marco Rubio will meet Israeli Prime Minister Benjamin Netanyahu in Israel on the weekend of February 28, the official said.

Feb 18 (Reuters) - The United States is in the process of withdrawing all of its roughly 1,000 troops from Syria, the Wall Street Journal reported on Wednesday, citing three U.S. officials.

Reuters could not immediately verify the report.

Last week, the U.S. military said it completed a withdrawal from a strategic base in Syria, handing it over to Syrian forces, in the latest sign of strengthening U.S.-Syrian ties that could enable an even larger American drawdown.

A top UN official warned Wednesday that steps by Israel to tighten control of areas of the West Bank administered by the Palestinian Authority amount to "gradual de facto annexation."

Since last week, Israel has approved a series of initiatives backed by far-right ministers to consolidate control over the West Bank where the Palestinians exercise limited autonomy under past deals.

President Donald Trump, shifting his tone yet again, warned Britain on Wednesday not to "give away" a key Indian Ocean base, saying it would be vital if the United States attacks Iran.

Trump, who is considering strikes on the Islamic republic, lashed out hours after the State Department offered the latest US support to British Prime Minister Keir Starmer's deal to return the Chagos Islands to Mauritius.

Under the agreement, Britain would instead pay to lease the strategic joint US-UK base at Diego Garcia for a century.

WASHINGTON, Feb 18 (Reuters) - U.S. President Donald Trump will host a Board of Peace meeting on Thursday in Washington, where he will announce that member states have pledged more than $5 billion for reconstruction and humanitarian efforts in Gaza, the White House said.

White House press secretary Karoline Leavitt told reporters that member states had committed to provide thousands of personnel for an international stabilization force for Gaza.

(Reporting by Steve Holland, writing by Andrea Shalal; Editing by Doina Chiacu)

Feb 18 (Reuters) - The United States is imposing visa restrictions on 18 Iranian officials and telecommunications industry leaders, the State Department said on Wednesday, in the latest such move against Tehran.

(Reporting by Ryan Patrick Jones and Costas Pitas)