The Export-Import Bank, the U.S. government agency that assists the sale of U.S. goods and services in other countries, authorized $291.5 million in loans, guarantees and insurance to support American exports to Venezuela, Israel and Mexico.

The Ex-Im Bank authorized $268.4 million in loans, guarantees and insurance to Venezuela in fiscal year 1987, which ended Sept. 30. The loans were intended to help U.S. exporters compete effectively in the Venezuelan market and to assist Venezuela's development and modernization programs.

In the past, the Ex-Im Bank has authorized a total of $6.3 billion in support of U.S. exports to Venezuela. In fiscal year 1986, Ex-Im Bank authorizations for Venezuela totaled $7.5 million.

An Ex-Im Bank-guaranteed loan of $13.1 million from Bankers Trust Co. of New York was to help finance the sale of $15 million in U.S. telecommunications production equipment to Israel. Tadiran Ltd. of Tel Aviv, Israel's largest electronics manufacturer, will use the equipment in projects for Israel's public and private telecommunications networks.

The projects involve installing cable television in Israel's major urban areas and supplying equipment for the national telecommunications network operated by BEZEQ and for various private networks.

U.S. suppliers involved in the export package include Atlanta Signal Corp. of Atlanta; R-Tec Systems of Bedford, Tex.; GTE Telecom of Northlake, Ill.; Motorola Inc. of Phoenix; and Intel International Ltd. of Santa Clara, Calif.

An Ex-Im Bank-guaranteed loan to Nacional Financiera, Mexico's national development bank, was to facilitate the export of $8.1 million in U.S. equipment and services to Mexico for modernizing a Ferrocarriles Nacionales de Mexico railroad switching yard.

WABCO Westinghouse International Co. of Pittsburgh will supply $6.5 million in computer equipment, terminals and switch machinery and $1.6 million in engineering services to help modernize the rail car classification yard at the Valle De Mexico terminal north of Mexico City.