Iran has signed a flurry of deals with Western companies over the past year since the easing of international sanctions on Tehran after an accord was reached over its nuclear programme.
However, tensions between the United States and Iran are on the rise again with the administration of President Donald Trump expected to impose fresh sanctions on multiple Iranian entities following Tehran's recent ballistic missile test.
Sources close to the matter say fresh sanctions will not violate the 2015 nuclear deal between Iran and the West.
But they are expected to add caution to decision making by many Western companies before they start investing money in Iran's economy.
Iran needs foreign investment for repairs and upgrading of its oil and gas fields. It also seeks the transfer of technology to its oil industry after a decade of isolation.
Below is a list of deal and Memorandum of Understanding (MoU) Iran has signed over the past year.
OIL AND GAS
* France's Total became in November 2016 the first oil major to sign a big deal with Tehran since the lifting of sanctions and agreed to help it develop the world's largest gas field, South Pars.
* Shell signed a provisional deal in December to develop Iranian oil and gas fields South Azadegan, Yadavaran and Kish in December. Chief Executive Officer Ben van Beurden said however that Shell has no near-term investment opportunities in Iran.
* Iran has named 29 companies from more than a dozen countries as being allowed to bid for oil and gas projects using the new, less restrictive contract model.
The firms include Shell, France's Total, Italy's Eni, Malaysia's Petronas and Russia's Gazprom and Lukoil, as well as companies from China, Austria, Japan and other countries.
* Russia's Zarubezhneft signed an MOU for a feasibility study on two joint fields in the west of the country.
* Norway's International Aker Solutions Company signed an MoU to modernise Iran's oil industry.
* Austria's OMV signed in May an MoU for projects located in the Zagros area in western Iran and the Fars field in the south.
* South Korean Daewoo Engineering and Construction (Daewoo E&C) signed an MoU to carry out construction of an oil refinery in Bandar Jask on the southern coast of Iran.
* Italy's Saipem signed MoUs to cooperate on pipeline projects, upgrading of refineries and development of Tous gas field in the northeastern province of Khorasan Razavi.
* Norwegian oil and gas company DNO said was the second western energy company after Total to sign a deal with Iran under which it agreed to study the development of the Changuleh oil field in western Iran.
* Lukoil, Russia's second biggest oil producer, hopes to reach a decision on developing two new oilfields in Iran.
* Germany's Siemens AG signed an MoU in May to overhaul equipment and facilities at Iran's oil operations and refineries.
* BASF's Wintershall oil and gas exploration subsidiary signed a memorandum of understanding (MOU) with the National Iranian Oil Company in April 2016.
* IranAir has ordered 100 aircraft from Airbus and the first plane has already been delivered.
* Boeing has a deal to sell 80 aircraft to IranAir and plans to arrange the lease of a further 29; the deal is not yet formally on the U.S. manufacturer's order book.
* European turboprop maker ATR, half-owned by Airbus and Leonardo, has provisionally agreed to sell 20 turboprop aircraft with options for a further 20.
French carmaker PSA Group was the Iranian market's biggest foreign player with nearly 30 percent of sales prior to its withdrawal in 2011 due to sanctions pressure.
In June 2016, PSA signed a 400 million euro production joint venture renewing the Peugeot brand's longstanding partnership with Iran Khodro to build Peugeot 208, 2008 and 301 models for the domestic market and export, starting in second half of 2017.
In October 2016, PSA finalised a new joint venture agreement with Citroen brand's historic partner SAIPA to invest 300 million euros in the production of Citroen models at Iran's Kashan plant, starting in 2018. Plans to open 150 dedicated Citroen outlets across Iran within five years.
German industrial group Siemens has ties with Iran going back to the 1867 Indo-European telegraph. It stopped doing new business in 2010 after being slammed for selling equipment that was used to spy on dissidents but maintains an office in Tehran. Recently, it has been in negotiations with Iran over an order for track technology and intercity trains that could be worth over 2 billion euros. It signed a contract to upgrade Iran's railway network in October.
Unconfirmed Iranian media reports last year said German chemicals giant BASF was in talks with Iranian officials about investing in a multi-billion-dollar petrochemical complex. BASF has declined to comment on these.
The company has said it welcomed the lifting of sanctions and was strictly adhering to international rules and agreements. BASF has a sales office in Iran and some polyurethane foams operations for finished products with "currently very limited commercial activities". It says it is observing the situation very closely.
Major global banks have so far shied away from handling Iranian-related business, citing the ongoing risk of violating ongoing U.S. sanctions. Among them is HSBC, which has said it has no intention of doing any new business involving Iran.
The Iranian central bank said in June 2016 that a few small European banks were among businesses that had links to the country, including Germany-based Europaeisch-Iranische Handelsbank AG and some small Italian lenders.
(Compiled by Bozorgmehr Sharafedin, Ron Bousso, Jonathan Saul, Georgina Prodhan, Tim Hepher and Laurence Frost, Editing by Parisa Hafezi/Ruth Pitchford)