By Lesley Wroughton BEIRUT, June 4 (Reuters) - U.S. Secretary of State John Kerry arrived in Leba**n on Wednesday, where he will pledge more aid to help Syria's neighbours deal with an influx of refugees and press Lebanese parliamentarians to swiftly choose a new president. Leba**n has been unable to agree on a consensus candidate for president, creating a political vacuum at a time when the country is struggling to contain domestic sectarian violence while also grappling with a flood of Syrian refugees and declining eco**mic growth. "It is an important period **w to show support for the Lebanese government," a senior State Department official told reporters. The State Department said Kerry will an**unce more than $290 million in additional aid for U.N. agencies and **n-governmental organizations working with the nearly 3 million Syrian refugees in Leba**n, Jordan, Turkey, Iraq and Egypt.