(Reuters) - U.S. Secretary of State Rex Tillerson on Thursday warned Lebanon over the Iran-backed Hezbollah group's growing arsenal and said the Shi'ite movement's involvement in regional conflicts threatened Lebanon's security.
Speaking alongside Lebanese Prime Minister Saad al-Hariri in a Beirut news conference, Tillerson also said the United States was engaging with Lebanon and Israel to ensure their border remained calm.
Israel regards Hezbollah as the biggest direct threat on its borders and has repeatedly struck it in Syria, where the group is fighting alongside President Bashar al-Assad in a civil war now entering its eighth year.
The heavily armed Shi'ite movement is part of the Lebanese coalition government led by Sunni Muslim politician Hariri, under a complex political system that promotes sectarian power-sharing.
"Hezbollah is not just a concern for the United States. The people of Lebanon should also be concerned about how Hezbollah’s actions and its growing arsenal bring unwanted and unhelpful scrutiny on Lebanon," Tillerson said.
"Hebollah's entanglement in regional conflicts threatens the security of Lebanon," he added during his visit, the first by a U.S. Secretary of State to Lebanon since 2014.
Israeli-Lebanese tensions have spiked in recent months because of Israeli plans to build a wall at the border, and because of Lebanon's decision to begin exploring for oil and gas in an offshore block in disputed waters.
Hezbollah, which the United States deems a terrorist organization, has increased its military strength since the last major conflict with Israel in 2006.
Tillerson urged Lebanese leaders to uphold the country's commitment to staying out of regional conflicts, a reference to Hezbollah's role in wars around the Middle East including in Syria.
Israel has accused Iran of seeking to set up weapons factories in Lebanon, and the Israeli military last month said the country had turned into one "large missile factory".
Lebanon is a big recipient of U.S. military support. Tillerson said Washington remained committed to supporting the Lebanese army and internal security forces.
When asked about the maritime border dispute with Israel, including Lebanese media reports that Washington had asked Beirut to give up a portion of sea it claims, Tillerson denied the reports.
"We will continue to be very engaged with both parties. We've asked no one to give up anything, rather we are looking for a solution," he said. "We are engaging the governments of both Lebanon and Israel to ensure Lebanon's southern border remains calm."