* Deals with U.S. firms, Trump visit buoys sentiment in Saudi
* Valuations suggest market has little room to rise
* Miner Ma'aden climbs after deal with GE
* Arabtec soars in Dubai after it wins big order for tower
* Gulf Navigation boosted by Q1 earnings
By Andrew Torchia
RIYADH, May 21 (Reuters) - Saudi Arabia's stock market outperformed a sluggish region on Sunday after U.S. and Saudi companies signed over $200 billion of deals during the visit to Riyadh by President Donald Trump.
Few of the deals involved listed Saudi companies, and many had been previously announced, or were merely memorandums of understanding that might never lead to concrete projects.
But the positive publicity around the agreements - and the warm welcome given to Trump amid talk of stronger diplomatic and economic ties between the countries - cheered some investors, and the Saudi stock index gained 0.8 percent.
"Sentiment is high because of the deals," said Talal Samhouri, head of asset management at Qatar's Amwal, though he added that from a fundamental point of view, the immediate outlook for the Saudi market was not particularly strong.
"The market is fairly valued, and we're coming to the summer months, where volumes become the lowest during the year," he said.
Mining company Ma'aden rose 1.9 percent. Among the deals announced on Saturday, GE said it would provide technology to Ma'aden to reduce its energy costs and boost efficiency.
Petrochemical companies were strong after oil prices rose sharply at the end of last week, with Saudi Basic Industries , the top petrochemical producer, gaining 1.5 percent.
Construction firm Khodari added 2.3 percent after it sold equipment in an auction for 43.1 million riyals ($11.5 million), making a profit of 17.4 million riyals.
Dubai's index edged up 0.3 percent. Builder Arabtec , the most heavily traded stock, rocketed 11 percent after saying it had won a 1.46 billion dirham ($398 million) contract to build a tower in central Dubai.
Gulf Navigation climbed 2.9 percent after reporting first-quarter net profit grew 39 percent from year ago to 8.8 million dirhams.
Abu Dhabi's index slipped 0.2 percent while Qatar dropped 0.5 percent, dragged down by a 1.5 percent slide in Qatar National Bank, the largest lender.
* The index gained 0.8 percent to 6,991 points.
* The index rose 0.3 percent to 3,386 points.
* The index fell 0.2 percent to 4,570 points.
* The index dropped 0.5 percent to 10,051 points.
* The index rose 0.2 percent to 12,975 points.
* The index added 0.5 percent to 6,760 points.
* The index edged down 0.02 percent to 1,309 points.
* The index edged 0.1 percent lower to 5,408 points. (Additional reporting by Celine Aswad; Editing by Elaine Hardcastle)