US Secretary of State Rex Tillerson met with EU and NATO leaders in Brussels on Tuesday. He reassured his 28 EU counterparts that the US remains committed to a strong partnership.

"The partnership between America and the European Union ... is based upon shared values, shared objectives for security and prosperity on both sides of the Atlantic and we remain committed to that,” he said at a meeting of NATO Ministers of Foreign Affairs.

This reaffirmation of US-EU ties comes at a time when many EU member states are concerned that US President Donald Trump's stark anti-NATO stance has undermined the transatlantic alliance.

'Strongest when allies'

Tillerson called on his EU and NATO partners to ramp up their defense budgets. 

"Our security is strongest when allies and partners shoulder their fair share of the burden," he said. "That's why we continue to call on others to increase their defense spending: It is towards a shared objective and serves everyone well."

In 2014, NATO member states agreed to stop defense budget cuts and pursue a target of spending 2 percent of GDP on defense within 10 years. So far only five NATO nations have hit the mark, including Estonia, Greece, UK, Poland and the US.

Read more: German Foreign Minister Gabriel questions NATO's defense spending target

Germany currently spends 1.2 percent of GDP on defense. German officials have expressed concern over the White House's demands, saying other factors should also be considered in the scope of the target. 

Controversial Issues: From Iran to Korea

In addition to defense spending, Tillerson discussed various topics including the Iran nuclear deal, the Middle East peace process and denuclearization of the Korean peninsula.

Tillerson lambasted Iran for its "destabilizing effect" in the Middle East, saying the US will continue to "take action" against the Islamic Republic. He asked for support from European partners in the matter.

President Trump officially "decertified" the nuclear deal with Iran in October, calling it "one of the worst and most one-sided transactions the United States has ever entered into."

European leaders were dismayed by President Trump's withdrawal from the agreement, which they consider an integral step towards preventing a Middle East arms race.

Read more: What is the Iran nuclear deal?

Days before Tillerson's European arrival in Brussels, a senior US State Department official underlined the main intent of the diplomatic tour, saying it aimed to "to reinforce President Trump's central message of shared responsibility in Europe and the global agenda that we're jointly managing with the EU, NATO, and European partners that includes DPRK, Syria, and issues related to Russia."

In addition to Brussels, Tillerson will be traveling to Vienna, to meet with OSCE officials, and Paris, to meet with senior French leaders to discuss issues in the Middle East and other areas of mutual concern.

ejw/ls (Reuters, dpa, AP, AFP)