The seven leaders at the 14th economic summit of industrial democracies agreed Tuesday to endorse new financial aid to the world's poorest nations and move toward curbing massive worldwide farm subsidies.

A final communique to be issued in the afternoon was to deal solely with economic issues, according to British officials who briefed reporters before the afternoon release of the document.Negotiators for the seven governments and the European Community, known as sherpas, worked until dawn put-ting the finishing touches on the 36-paragraph document. The talks were complicated and often difficult, said one British official, who asked not to be named.

"You have no idea how long it can take over one semi-colon," the official said.

But President Reagan - attending his eighth and final economic summit, and most likely making his final foreign trip as president - stressed harmony and unity as the leaders presented an upbeat assessment of the global economy in three days of talks.

Reagan agreed with the leaders of Canada, Britain, France, West Germany, Italy and Japan not to include in the final document political declarations such as one encouraging new economic links with the Soviet Bloc.

The communique, formulated in three days of meetings at the 14th annual summit, also would contain language promoting efforts to remove state control of economies through tax cuts, deregulation and the sale of government enterprises to the private sector, the British officials said.

"There is a developing consensus that structural reforms are key to improving medium term growth of industrialized nations," he said.

The communique was to confirm the creation of a commodity price indicator, designed to help the summit partners, also known as the Group of Seven, monitor global economic conditions, as part of continuing coordination of economic policies. The components of the commodity indicator will be kept confidential, according to Japanese officials, but gold was expected to be included in the index.

The seven leaders also endorsed efforts to liberalize international trade - including agricultural trade - at the conference of all trading nations in Montreal in December, British officials said. Those talks will be held under the authority of the General Agreement on Tariffs and Trade.

Japanese officials said the communique will call for improved dialogue with "newly industrialized economies," apparently referring to Taiwan, South Korea, Singapore and other emerging economic nations.

Reagan continued to receive warm tributes from his fellow leaders.

"Ronald Reagan is viewed by all of us with deep affection," said Canadian Prime Minister Brian Mulroney, the summit host, as he walked into the leaders' final plenary session early Tuesday.

A political statement released Monday congratulated Reagan by name for signing the Intermediate Nuclear Forces treaty with the Soviet Union.

Monday's political declaration also called for unified international efforts to combat terrorism, especially air piracy, and international drug trafficking.

The United States, however, agreed to endorse a new program of relieving the debt burden of the poorest nations, mostly in sub-Sahara Africa, British officials said.

Treasury Secretary James Baker has emphasized the United States could not take much part in the plan because of budgetary and legal constraints, but that it will not stand in the way of other creditor nations to help debtors.