Israel and the Gulf state of Bahrain have reached a landmark deal to fully normalise their relations, US President Donald Trump has announced.
"The second Arab country to make peace with Israel in 30 days," he tweeted.
For decades, most Arab states have boycotted Israel, insisting they would only establish ties after the Palestinian dispute was settled.
But last month the United Arab Emirates (UAE) agreed to normalise its relationship with Israel.
There had been much speculation that Bahrain might follow suit.
Trump, who presented his Middle East peace plan in January supporting a two-state solution between Israel and the Palestinians, has helped broker both agreements.
The Gulf state has become only the fourth Arab country in the Middle East to recognise Israel since its founding in 1948. The others are Egypt and Jordan.
"Another historic breakthrough today!" Mr Trump wrote, adding: "Our two GREAT friends Israel and the Kingdom of Bahrain agree to a Peace Deal."
The president also posted on Twitter a copy of a joint statement between the US, Bahrain and Israel.
Prior to the UAE announcement in August, Israel had had no diplomatic relations with Gulf Arab countries. More recently, shared worries over Iran have led to unofficial contacts between them.
Last month saw the first official flight from Israel to the UAE, which was seen as a major step in normalising relations.
President Trump's son-in-law and senior adviser Jared Kushner, who was on the plane, described the UAE deal as having "the ability to change the whole course of the Middle East".
Bahrain last week said it would allow flights between Israel and the UAE to use its airspace.
Mr Trump is due to host a ceremony next Tuesday celebrating the Israel-UAE Deal.
In 1999, Mauritania, a member of the Arab League in north-west Africa, established diplomatic relations with Israel - but severed ties in 2010.-BBC