The second element is the capability to put some producer countries (competitors) out of the market by imposing secondary sanctions. This is exactly what is happening with Iran. Only a couple of countries in the world can overlap this constraint.
The third element, which is not new, is the financial sector. Since the majority of the oil operations are conducted in U.S. dollars, the influence of the country whose currency is used is undeniable. Even though we can consider particular arrangements such as those between Russia and China, or India and Iran or even the unborn European Instrument in Support of Trade Exchanges, the fact is that it is hard to work outside the U.S. dollar-driven market.
The combination of those three elements had an impact on OPEC policies. This institution is losing influence. A recognition of its eroding power was the establishment of the OPEC+ with the inclusion of non-OPEC members' producers to increase its global impact on the markets. But at this moment we are witnessing the limitations of this agreement since even the OPEC (14) and plus countries (10) cannot control oil prices.
The current situation shows that resources, oil wells, in this case, should be complemented with financial, technological and military capabilities in order to become influential. Otherwise, oil producer countries cannot control the price of their main export commodity.
The paradox, actually, is that they are becoming more dependent on the United States and, at the same time, are becoming more dependent on the importing countries, China for example. In a global market with a diminishing pool of buyers, multilateral arrangements are enclosed by unilateral needs. If the economy is based on the export of one product this dependency is higher.
At this moment, two of the most significant global security issues, the U.S.- China escalating trade war and U.S.-Iran tensions, are led by Washington where the Trump administration and its policy of "America First" is not interested in reaching agreements but on imposing unilateral policies. Institutional and multilateral agreements are not significant enough in a world dominated by unilateralism.
In this general international framework, OPEC and OPEC+ need to reconsider their policies aimed at influencing market trends. Oil cut agreements are no longer as influential as they were in the past.