Since 1974, the UN Disengagement Observer Force (UNDOF) has monitored the ceasefire between Syria and Israel, and patrolled the demarcation line between Syrian and Israeli-controlled areas of the Golan.
Trump's comments come as Secretary of State Mike Pompeo is in Israel and a week ahead of Israeli Prime Minister Benjamin Netanyahu's visit to Washington to visit the White House and address the AIPAC lobby's annual meeting.
Syria tried to regain the Heights in the 1973 Middle East war, but was thwarted.
When Trump recognized Jerusalem as Israel's capital, he said it did not determine the city's final borders.
Israel captured the Golan, a strategic plateau overlooking northern Israel, from Syria in the 1967 Mideast war and annexed the area in 1981.
Richard Haass, a former senior State Department official who is president of the Council on Foreign Relations, said in a tweet he strongly disagreed with Trump's Golan decision.
"We all found out by tweet", one Israeli official said.
"After 52 years it is time for the United States to fully recognize Israel's Sovereignty over the Golan Heights, which is of critical strategic and security importance to the State of Israel and Regional Stability!" he wrote. "The President has made clear his support for Netanyahu".
Netanyahu is battling for his political survival against both a strong challenger in centrist candidate Benny Gantz and against plans by Israel's attorney-general to indict the prime minister, now in his fourth term, in three corruption cases.
The Trump decision to recognize the Golan now gives Netanyahu a significant boost before the election, but will also also trigger criticism that the U.S. president is blatantly meddling in the Israeli elections.
Following are excerpts from Netanyahu's remarks at the joint statements with U.S. Secretary of State Mike Pompeo in Jerusalem Thursday evening, regarding Trump's declaration. Responding on Twitter, Netanyahu thanked Trump for "boldly recognizing" Israel's sovereignty over the land.
More than 40,000 people live on the Israeli-occupied Golan, more than half of them Druze residents - an Arab minority who practice an offshoot of Islam.
Trump, whose decision past year to move the USA embassy to Jerusalem from Tel Aviv angered Palestinians, faced some criticism for his latest move.
Israel has carried out hundreds of air strikes there against what it says are Iranian and Hezbollah targets. 'All of you can imagine what would have happened if Israel were not in the Golan: We would have Iran on the shores of the Sea of Galilee'. His son-in-law, Jared Kushner, is in charge of brokering a peace deal between Israel and Palestine.
Administration officials said that National Security Advisor John Bolton was instrumental to the decision, after visiting Israel in January to assure officials there that the United States would not abandon them in Syria despite Trump's sudden withdrawal of troops from the battlefield. Those states, however, have long rejected Israel's annexation of the Golan.