"Yesterday I met publicly with the Foreign Minister of Bahrain" Sheikh Khalid bin Ahmed Al Khalifa, Katz said in a tweet.
Referring to Benjamin Netanyahu, Katz added: "I will continue to work with (the Israeli Prime Minister) to advance Israel's relations with the Gulf countries."
Israel has diplomatic relations with only two Arab countries - Egypt and Jordan - but common concerns over Iran have brought it closer to Gulf nations in recent years.
In a photograph accompanying the tweet the two foreign ministers appear side by side, smiling.
According to an Israeli Foreign Ministry statement, the "meeting was coordinated behind the scenes by the US State Department as part of a conference on religious liberty organised in Washington by US Secretary of State Mike Pompeo".
The two men "addressed the subject of Iran and regional threats as well as cooperation between states and agreed to continue...," it added.
Gulf Arab nations have increasingly found common cause with Israel due to their shared hostility towards Iran. Tehran is accused of wanting to extend its influence in the region and of seeking to acquire nuclear weapons.
The meeting comes at a time of mounting tensions in the Gulf region between the US and Iran which has been slapped with a raft of sanctions by the Trump administration.
On Thursday, the US military shot down an Iranian drone on that came within 1,000 yards of one of its naval vessels in the Strait of Hormuz, President Donald Trump said.
Last week, a British warship in the Gulf warned off armed Iranian boats that tried to stop a UK supertanker. London has since announced the deployment of two more warships to the Gulf region for the coming months.
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