Israel was admitted as the 59th UN member on 11 May 1949 and subsequently joined all the nonregional specialized agencies. It is also a permanent observer with the OAS and a member of the WTO. During the 1970s and early 1980s, Arab governments sought through the "oil weapon" to isolate Israel diplomatically and economically, but Israel's 1979 peace treaty with Egypt helped ease some of the pressure. The United States is Israel's major political, economic, and military ally. A number of African countries reestablished diplomatic relations with Israel in the 1980s; these ties had been broken in 1973, following the Arab-Israeli war. After signing peace accords with the Palestinians in 1993 and 1994, Israel opened liaison and trade missions in certain Arab countries, including Qatar and Oman. Israel also signed a peace agreement with Jordan in 1994, and the two nations exchanged ambassadors in 1995. Violence between Israel and the Palestinians resulting from the intifada that began in September 2000 increased tensions with the Arab world. In November 2002, 18 of the 22 members of the Arab League agreed to reactivate a half-century-old ban on trade with Israel.