The Belgian government, ended several months of hesitation and decided early today to begin the immediate deployment of cruise nuclear missiles as scheduled by NATO, government sources said.

The Belgian Cabinet made the decision after debating the issue for several hours Thursday night, sources said.

Sixteen cruise missiles will be deployed within the next several weeks at an air base near the southern town of Florennes, followed by an additional 32 missiles by the end of 1987, the sources said.

"The engagements to NATO will be respected," said Belgian Defense Minister Alfred Vreven, after leaving the Cabinet meeting.

The decision leaves the Netherlands as the only country that has not decided to deploy intermediate range missiles under NATO's 1979 modernization program. The other countries which have begun deployment are West Germany, Italy and Britain.

Belgium's initial refusal to deploy the missiles on schedule had strained the Atlantic Alliance and threatened to bolster sentiment in some Western European countries for a moratorium on deployment under renewed Soviet pressure.

NATO decided in 1979 to link deployment of a new generation of intermediate-range missiles to negotiations with the Soviet Union.

The Soviets, however, walked out of arms-reduction talks in Geneva in late 1983 after NATO actually began deployment of the Pershing II missiles in West Germany, and cruise missiles in Britain and Italy, vowing not to return until the missiles were withdrawn.

During the fall of 1984, Moscow began dropping references in public statements to the new NATO missiles and last January, after a meeting between Secretary of State George P. Schultz and Soviet Foreign Minister Andrei Gromyko, the Soviets agreed to resume talks, which opened this week in Geneva. The U.S. emphasis on its Strategic Defense Inititiative, commonly known as "Star Wars," has been cited by observers as a possible factor in persuading the Soviets to begin talks anew.

Belgian Prime Minister Wilfried Martens met with President Reagan in Washington in January, but Reagan was unable to secure a firm commitment from Martens to deploy the missiles.

At that time the most that Reagan could elicit from Martens was a pledge that Belgium remained commited to NATO's decision to deploy the full range of 572 Pershing and cruise missiles by the end of 1987 unless the Soviet Union agrees to reduce its arsenal of SS20 medium-range missiles.

Prime Minister Martens will present the deployment decision to Parliament Friday along with the government's budget program, the sources said.

The opposition Socialist Party, which is opposed to deployment, can call for a vote of confidence in the government, but it cannot ask for a separate vote on the missile decision, a government spokesman said. The government has a six-vote majority in Parliament.

The Belgian decision had been delayed by pressure within Martens' own Christian People's Party to put off deployment in order to give the renewed U.S.-Soviet arms talks a chance of success. Some party members also feared the missile issue could cause the defeat of the government in elections scheduled later this year.

The United States and other NATO nations urged Belgium to follow the NATO timetable to demonstrate alliance solidarity as the arms talks got under way.